New Build - Thoughts on the new RPM based Throttle Response Curves

~~Jack B~~ · 20 January 10, 18:53

The new iRacing Build came out this morning a couple of hours ago. Lot's of new features. Since non-members can't see the iRacing forums, I thought I'd cut/paste the respones to the RPM based Throttle Response curves.

What is this new feature? Well, each car had their throttle response adjusted to match real life HP delivered to the wheels based upon whatever amount of RPM's were being run in each individual gear. Basically, if you push down some amount on the gas pedal at 5,000 RPM's in 1st gear, you get a different response than if you push down on the gas pedal at 5,000 RPM's in 6th gear. So, it's combining RPM and gear ratios per car dynamically to generate the throttle curves. It seems to make a difference. I'm not sure how many sims have taken Throttle curves it to this level, but I'm glad iRacing did.

I removed the driver names (for their privacy) and separated each response with === I might do this for some other things if any non-members on No Grip care to see the iRacing forum responses on some important topics/changes in the new build.

===

So how is it. For us stuck at work. grrr

===

Ffffffuuuuuuuuu!!!!!

===

Awesome. It completely changes the feel of the cars; in a great way.

===

Not sure exactly because I am not good enough to tell much, but the legends race I was in I just ran 4 of the 5 fastest laps ever at Lanier. Hopefully I will have time to try the COT later tonight.

===

more info? please

===

So far I've only had time for a few laps in the Mazda but it does feel different...but IMO not a lot. I can't tell if it's the throttle thing or the other physics changes in this build, probably some of all.

===

Well I'm not sure if its placebo, but it feels much much better for me

I can control the power at the lower range better. Good job iRacing

===

The response in the skippy tests I ran seems like wow...

===

Yeah, I can definitely see and feel the difference. I love it.

===

Ditto. Feels much more like what I'm used to from the physical cars I've driven.

===

Had to adjust throttle control from lastnight to this morning in the trucks at Texas.

Good Stuff ! ! !

===

So far every car I've tried feels better, in every aspect you'd expect throttle response to play a part in. Opposite lock + feathering the throttle feels better, lift-off oversteer isn't so dramatic, gas under braking isn't as necessary, etc...

===

I noticed it leaving pit road at Texas in the trucks, I couldn't mash it. I also picked up 3 tenths over my time from last night.

===

i also picked up three tenths at texas.. i'm a HUGE fan of the new throttle curve.. great job iracing on this one.. i would say this is THE BIGGEST physics change since we've started.. i too am stuck at work.. but i had to sneak away to give it a try.. and like i said earlier went from .3's alone to flats alone, with no other changed.. it felt very lifelike and much more controllable.. and more to come next week.. damn this is better than christmas!!!

very satisfied customer...
rr

===

i love it...makes the silver crown that much cooler...now anymore then 25% throttle and i'm spinning out!

===

I haven't got to test many cars yet, but in the skippy wow does it sure feel more comfortable driving it. Your not sliding it unrealistically anymore, I am not sure how to quiet explain it, but you feel like you have 4 wheels under you, the overall feel and throttle response is way better.

It's one of those thing's you just gotta try, Overall I think this is going to make people really enjoy driving again.

===

There is definitely a difference. Made it through the indy car and nationwide car so far, setting up car controller profiles for each. I've been in Iracing limbo for for much of the 2009 season, but updates like this certainly are a step in the right direction. Feels a lot more like real life race cars I've driven.

===

Yep I'm very happy with this single change too. It feels much more authentic (I can't really say if it is with no RL track time..) and makes corner exit feel sublime.

Great job guys.

===

Wow, huge difference. Feels much more like the real racecars I have driven. Before it was 90% of the power in the last 10% of throttle travel, and now its much more linear as it should be. Great work iRacing!

===

Have to agree with all here. Hitting the throttle now feels like your dumping a shedload of horsepower on the rear wheels which is great

===

"gas under braking isn't as necessary, etc... "
Can anyone expand on the above quote a bit more?

C6r now has a lot more power...Top speeds @ Daytona are now 182mph +

New build seems very nice iRacing...good job!!!

===

Daytona is pretty close to sea level...

===

I dont know if this is related to the update or im having equipment problems but the FF in my wheel decreased drastically...and i didnt change any settings. Kinda odd.

Going to investigate the matter more. Will report back.

===

Man I'm starting to feel really sick. I think I need to go home early today.

===

I noticed that the update reset my FFB strength setting. Check the setting in the options menu. I changed it back to my previous setting and it feels OK.

Only driven the Mazda so far...

It does feel a lot better. I don't find it harder to control at low speeds. The rear wheels will spin a little easier, but I don't think that's due to the throttle response change. I think it's the new tire modeling.

The other thing I noticed right off the bat is the way the FFB feels while the car is sitting still. You can feel the front tires squirm as you turn the steering wheel.

The biggest thing I noticed was how much easier it is to control a high speed slide where the car gets loose. You can feather the throttle and feel the car respond. Before, the car just felt dead in that situation. Feathering the throttle didn't seem to have any effect at all.

===

Is it possible for the Daytona Prototype to do a burnout now? I know from personally watching them pull out of the pits that it is possible in the real car. The standing start issue in this car needs to be fixed.

===

> C6r now has a lot more power...Top speeds @ Daytona
> are now 182mph +
>
> New build seems very nice iRacing...good job!!!
>
>
> GA

I dont like this new throttle with Corvette, its even harder to drive than before.
I mean, if i push my gas pedal like 1 cm and keep it there, the car is revving to the limiter, wtf is this??? With a car which was already way too slippery on the exits..
You have to be even more cautious when exciting the corners, i dont like this at all..

It cant be like one throttle response tweak fits all cars, it seems to fit Skippy, but with Vette... big no no.. at least no for me.
If this is left like this, i cant drive the Vette no more.

===

I would suggest setup changes to your C6r...Try to improve the rear grip in the garage

===

i love the new throttle for the vette. i just went from running high 45's down to low 43's. the car just feels more natural now.

===

"gas under braking isn't as necessary, etc... " Can anyone expand on the above quote a bit more?

Throttle is more responsive at less travel, so you don't have to press down on the gas as much as before in order to balance the car.

===

Only messed with a few cars but this change definetely "feels" right.

I will also add that I have ZERO real life experience in anything bigger than a go kart so take it for what it is but I think this is a step in the right direction.

===

I'm gonna guess and say that this will help the folks who really have the skills to work the pedals with the Heel / Toe technique.

===

I picked up 3 tenths in the COT at Homestead. The car definitely feels looser. The first thing I thought of when the car started pushing was D.W. once saying when he had a real tight car, he'd stab the throttle real quick to help it turn better. I've never seen that work in the COT as well as it does now.

===

Just tested it out on the truck and wow. It actually feels like a race car with some horsepower.

Great job iRacing! Loving this new build!

PS, go and grenade your engine. It's funny. Mine made a popping noise and and a huge puff of smoke can pouring out as soon as it died.

===

> I picked up 3 tenths in the COT at Homestead. The
> car definitely feels looser. The first thing I
> thought of when the car started pushing was D.W. once
> saying when he had a real tight car, he'd stab the
> throttle real quick to help it turn better. I've
> never seen that work in the COT as well as it does
> now.

lol. at first I thought great, I'll be faster. But then again, so will everyone else

===

> Man I'm starting to feel really sick. I think I need
> to go home early today.

Yeah I might have to duck out too.

===

I can't wait to go home and try the new build out! I like seeing all the positive feedback from some of the respected people in the community. They know their stuff so I trust this is a good update. Thanks for the updates guys!

I'm here till 6....wow thats a while away
===
Well, between my last comment and this one... I went out and got a G27. Wow, big step up from the Momo I've been running for years...

Now the throttle changes feel reeeaaally good.
===
Late Model at Martinsville and Phoenix feels great. Very progressive sideslip angle buildup. You can easily go past the optimum sideslip and still control it. At this point it seems like you have to hit that peak to be fast, but the car is easier to control at and over the peak limit.

~~Empty Box~~ · 20 January 10, 18:59

I heard about this before I left and it seemed very interesting. I've always noticed that you needed to hold the pedal at about 75% throttle to maintain (just maintain) speed. Which, would make normal street cars funny on the highway (Take that eco nerds!)

So is this just an update or is it the end of season week 13 next season build?

~~Jack B~~ · 20 January 10, 19:03

Quote:

Originally Posted by Empty Box

I heard about this before I left and it seemed very interesting. I've always noticed that you needed to hold the pedal at about 75% throttle to maintain (just maintain) speed. Which, would make normal street cars funny on the highway (Take that eco nerds!)

So is this just an update or is it the end of season week 13 next season build?

This is the new build. It's almost one week earlier than normal, (we're in the final week of the season) because the World Cup of Inagural iRacing Competition starts next Tues (I think it's Tues or Wed) and they wanted enough time to fix and issues before the competition starts.

The left out 3 things though, which will be mini-updates in the next 1 to 4 weeks.

1. I think it was Aero changes to the Trucks, COT and NW.
2. Some of the tire model tweaks.
3. The transmission model changes.

AllanGP · 20 January 10, 21:26

Well after a week at Lime Rock just blew away my previous best lap at Laguna in the Slowstice by 0.6 sec in just 30mins getting used to the car there again.

More front end grip, better feed back, nice one!!

Allan

~~Jack B~~ · 20 January 10, 21:48

Quote:

Originally Posted by AllanGP

Well after a week at Lime Rock just blew away my previous best lap at Laguna in the Slowstice by 0.6 sec in just 30mins getting used to the car there again.

More front end grip, better feed back, nice one!!

Allan

Yeah, I ran about 8 laps with the Skippy at Watkins Glen Boot and improved my best time by about the same amount. It seemed more predictable and fit like a glove. I was much more consistent too. The car felt so good to drive.

I've always loved the Skippy, but this felt better than ever. Hope I can find some free time for racing this week!

merlin · 21 January 10, 09:31

not sure if they got the transmission model changes in to this build.but personally i love the consictancy of the newish tires on the skippy, upto yesterday i could not get around mosport incident free then after the change first race started 14th finished 4th

amazing what you can get by just plugging away at your own speed

AllanGP · 21 January 10, 13:05

Should have said before - off road excursions (in the Solstice at Laguna) - of which I have many

- seem a lot more controllable as well.

Plus sensation when driving in gravel seems more realistic??

Now 0.7 quicker and not really strung a proper lap together yet.

Also I like the way the nose moves up as you set off from standstill and the down change "blip" is better and more audible.

Plus I got the option to re-calibrate my G25 so feedback is better with no issues as stated above.

Allan

Mahjik · 21 January 10, 21:40

I ran several laps last night at Daytona with the C6R. The good: I'm about 1.5 seconds faster with the update. The bad: so is everyone else.

The lower end power is now trickier to put down on the Vette. TBH, this is closer to how I though the Vette was going to be when it was initially released. As mentioned, the throttle blips now are much lower compared to what was needed before. I'm still trying to decide if that's a good thing or not.

I didn't really notice much else with the handling, but the car still feels good.

~~Empty Box~~ · 21 January 10, 21:58

Woa.

First off - I like the fact that no longer do I feel like I'm almost full throttle to maintain speed. That's good.

But, UMMMMmmmm...... Mazda? I can't drive the thing now!

~~Jack B~~ · 22 January 10, 01:47

Grant Reeve from iRacing decided to post and explain a bit more about the new iRacing Throttle Curve... If you ever wonder if all sims are created equal, they aren't. And even the simpliest things can get pretty complex.

Here is Grant's explanation of the old and new throttle curves. Not sure what Mario Kart uses, but it's probably not this...

=============================

The old throttle response curve was a simple y = x^2, which was done like a million billion years ago, way before I ever arrived at Papyrus in 98 and no one has ever thought to go back and look at it. We would know for all those cars we've modelled for the last 15-20 years what the full throttle dyno curve looks like, and what the off throttle engine braking looks like, but how the engine responds in between those two extremes I guess was never realized to be quite an important driving characteristic.

I believe the original logic was that y=x^2 approximates the shape of a 1-cosine curve from 0 to 90 degrees which was supposed to vaguely model the opening of the butterfly valve in the throttle body (but in my mind I'd expect that the butterfly valve opening would be better modelled with a sine curve than 1-cosine, and that would have been a far better match to the actual response)

The new throttle response curves are based on several sets of real vehicle data. One of the cars we model even has dyno information for full rpm pulls at every 10% of throttle position. By comparing how the engine power at any given rpm varies with throttle application I came up with an approximating function that sort of looks like the average of all the data we have.

At very small throttle openings, the airflow is pretty much choked to a fixed amount, so regardless of engine rpm it's only getting a fixed amount of air to burn for power output. Thus the initial (first 10-15% or so) throttle response regardless of rpm is kind of proportional to power output.

But at full throttle, the power output is limited by how much air the engine can pump. At low rpms the engine can't flow much air so it very quickly saturates it's power output, which is why at low rpm you feel like you're getting 80-90% of engine power by 40-50% of throttle, and the rest of the throttle travel feels very unresponsive. But at high rpm the motor can pump a whole lot of air, so the power output keeps increasing the further you get into the throttle.

Eventually you start running into limitations of how much air the throttle body can flow when wide open, and into limitations of the engine's volumetric efficiency at pumping air at very high rpm, which causes the throttle response to still flatten off as you get towards 80-90% even at max rpm.

It's quite likely that every engine in existance has subtley difference throttle response based on various build characteristics, but we're just giving them all the same response curve for now based on what their rev limit is.

First time I tried the new curves - like most of you guys have noticed - it immediately felt incredibly more natural - even the Spec Racer (which I like to call a Death Trap) was suddenly a whole lot more controllable and drivable. So, yeah, it does seem that it's pretty important to model what happens in between 0% and 100%

================

So there you go. When iRacing decides to work on something they don't kid around. Can't wait to see how the new Transmission Modeling works out...

~~Roush9~~ · 22 January 10, 01:54

I've only tried the ImpA, but it felt exactly the same to me. Might do some Vette tonight to see if I can notice anything.

moppenheimer · 22 January 10, 19:21

Quote:

Originally Posted by Roush9

I've only tried the ImpA, but it felt exactly the same to me. Might do some Vette tonight to see if I can notice anything.

Road cars are much different, the Dp and Vette are much harder to manage out of a corner

~~Empty Box~~ · 22 January 10, 20:26

I will admit.

I looped the Mazda.

I had NEVER done that before the other day. It actually feels like it has some power - it's more sensitive. I honestly feel like the throttle sensitivity has been jacked through the roof, but looking at the bars show it isn't. It's nice.

I don't think it'll make to big of a difference on the Oval cars though seeing how your not on and off the throttle near as much. Plus you can actually stab the gas to get it to turn a little bit finally.

marc1111 · 26 January 10, 16:50

Thanks for posting that Jack B. I missed that in the forums - great info! Yet another example of the thinking that iRacing puts into the minor but important details of their sim.

My reaction to the throttle response now is that it is absolutely fantastic and feels much more realistic. The cars are much more responsive throughout the powerband and you really have to modulate the throttle more precisely at lower ranges of throttle application. It's great!!

I've also noticed that I now use VERY little throttle while braking compared to what I did before. The car responds the way you think it should if you apply 25% throttle, ie it pushes!!!. I suspect this may have squashed throttle-while-braking debate that has bothered many iRacers (including me) since the sim was released.

20 January 10, 18:53	#1
~~Jack B~~ Banned Join Date: May 2008 Age: 55	New Build - Thoughts on the new RPM based Throttle Response Curves The new iRacing Build came out this morning a couple of hours ago. Lot's of new features. Since non-members can't see the iRacing forums, I thought I'd cut/paste the respones to the RPM based Throttle Response curves. What is this new feature? Well, each car had their throttle response adjusted to match real life HP delivered to the wheels based upon whatever amount of RPM's were being run in each individual gear. Basically, if you push down some amount on the gas pedal at 5,000 RPM's in 1st gear, you get a different response than if you push down on the gas pedal at 5,000 RPM's in 6th gear. So, it's combining RPM and gear ratios per car dynamically to generate the throttle curves. It seems to make a difference. I'm not sure how many sims have taken Throttle curves it to this level, but I'm glad iRacing did. I removed the driver names (for their privacy) and separated each response with === I might do this for some other things if any non-members on No Grip care to see the iRacing forum responses on some important topics/changes in the new build. === So how is it. For us stuck at work. grrr === Ffffffuuuuuuuuu!!!!! === Awesome. It completely changes the feel of the cars; in a great way. === Not sure exactly because I am not good enough to tell much, but the legends race I was in I just ran 4 of the 5 fastest laps ever at Lanier. Hopefully I will have time to try the COT later tonight. === more info? please === So far I've only had time for a few laps in the Mazda but it does feel different...but IMO not a lot. I can't tell if it's the throttle thing or the other physics changes in this build, probably some of all. === Well I'm not sure if its placebo, but it feels much much better for me I can control the power at the lower range better. Good job iRacing === The response in the skippy tests I ran seems like wow... === Yeah, I can definitely see and feel the difference. I love it. === Ditto. Feels much more like what I'm used to from the physical cars I've driven. === Had to adjust throttle control from lastnight to this morning in the trucks at Texas. Good Stuff ! ! ! === So far every car I've tried feels better, in every aspect you'd expect throttle response to play a part in. Opposite lock + feathering the throttle feels better, lift-off oversteer isn't so dramatic, gas under braking isn't as necessary, etc... === I noticed it leaving pit road at Texas in the trucks, I couldn't mash it. I also picked up 3 tenths over my time from last night. === i also picked up three tenths at texas.. i'm a HUGE fan of the new throttle curve.. great job iracing on this one.. i would say this is THE BIGGEST physics change since we've started.. i too am stuck at work.. but i had to sneak away to give it a try.. and like i said earlier went from .3's alone to flats alone, with no other changed.. it felt very lifelike and much more controllable.. and more to come next week.. damn this is better than christmas!!! very satisfied customer... rr === i love it...makes the silver crown that much cooler...now anymore then 25% throttle and i'm spinning out! === I haven't got to test many cars yet, but in the skippy wow does it sure feel more comfortable driving it. Your not sliding it unrealistically anymore, I am not sure how to quiet explain it, but you feel like you have 4 wheels under you, the overall feel and throttle response is way better. It's one of those thing's you just gotta try, Overall I think this is going to make people really enjoy driving again. === There is definitely a difference. Made it through the indy car and nationwide car so far, setting up car controller profiles for each. I've been in Iracing limbo for for much of the 2009 season, but updates like this certainly are a step in the right direction. Feels a lot more like real life race cars I've driven. === Yep I'm very happy with this single change too. It feels much more authentic (I can't really say if it is with no RL track time..) and makes corner exit feel sublime. Great job guys. === Wow, huge difference. Feels much more like the real racecars I have driven. Before it was 90% of the power in the last 10% of throttle travel, and now its much more linear as it should be. Great work iRacing! === Have to agree with all here. Hitting the throttle now feels like your dumping a shedload of horsepower on the rear wheels which is great === "gas under braking isn't as necessary, etc... " Can anyone expand on the above quote a bit more? C6r now has a lot more power...Top speeds @ Daytona are now 182mph + New build seems very nice iRacing...good job!!! === Daytona is pretty close to sea level... === I dont know if this is related to the update or im having equipment problems but the FF in my wheel decreased drastically...and i didnt change any settings. Kinda odd. Going to investigate the matter more. Will report back. === Man I'm starting to feel really sick. I think I need to go home early today. === I noticed that the update reset my FFB strength setting. Check the setting in the options menu. I changed it back to my previous setting and it feels OK. Only driven the Mazda so far... It does feel a lot better. I don't find it harder to control at low speeds. The rear wheels will spin a little easier, but I don't think that's due to the throttle response change. I think it's the new tire modeling. The other thing I noticed right off the bat is the way the FFB feels while the car is sitting still. You can feel the front tires squirm as you turn the steering wheel. The biggest thing I noticed was how much easier it is to control a high speed slide where the car gets loose. You can feather the throttle and feel the car respond. Before, the car just felt dead in that situation. Feathering the throttle didn't seem to have any effect at all. === Is it possible for the Daytona Prototype to do a burnout now? I know from personally watching them pull out of the pits that it is possible in the real car. The standing start issue in this car needs to be fixed. === > C6r now has a lot more power...Top speeds @ Daytona > are now 182mph + > > New build seems very nice iRacing...good job!!! > > > GA I dont like this new throttle with Corvette, its even harder to drive than before. I mean, if i push my gas pedal like 1 cm and keep it there, the car is revving to the limiter, wtf is this??? With a car which was already way too slippery on the exits.. You have to be even more cautious when exciting the corners, i dont like this at all.. It cant be like one throttle response tweak fits all cars, it seems to fit Skippy, but with Vette... big no no.. at least no for me. If this is left like this, i cant drive the Vette no more. === I would suggest setup changes to your C6r...Try to improve the rear grip in the garage === i love the new throttle for the vette. i just went from running high 45's down to low 43's. the car just feels more natural now. === "gas under braking isn't as necessary, etc... " Can anyone expand on the above quote a bit more? Throttle is more responsive at less travel, so you don't have to press down on the gas as much as before in order to balance the car. === Only messed with a few cars but this change definetely "feels" right. I will also add that I have ZERO real life experience in anything bigger than a go kart so take it for what it is but I think this is a step in the right direction. === I'm gonna guess and say that this will help the folks who really have the skills to work the pedals with the Heel / Toe technique. === I picked up 3 tenths in the COT at Homestead. The car definitely feels looser. The first thing I thought of when the car started pushing was D.W. once saying when he had a real tight car, he'd stab the throttle real quick to help it turn better. I've never seen that work in the COT as well as it does now. === Just tested it out on the truck and wow. It actually feels like a race car with some horsepower. Great job iRacing! Loving this new build! PS, go and grenade your engine. It's funny. Mine made a popping noise and and a huge puff of smoke can pouring out as soon as it died. === > I picked up 3 tenths in the COT at Homestead. The > car definitely feels looser. The first thing I > thought of when the car started pushing was D.W. once > saying when he had a real tight car, he'd stab the > throttle real quick to help it turn better. I've > never seen that work in the COT as well as it does > now. lol. at first I thought great, I'll be faster. But then again, so will everyone else === > Man I'm starting to feel really sick. I think I need > to go home early today. Yeah I might have to duck out too. === I can't wait to go home and try the new build out! I like seeing all the positive feedback from some of the respected people in the community. They know their stuff so I trust this is a good update. Thanks for the updates guys! I'm here till 6....wow thats a while away === Well, between my last comment and this one... I went out and got a G27. Wow, big step up from the Momo I've been running for years... Now the throttle changes feel reeeaaally good. === Late Model at Martinsville and Phoenix feels great. Very progressive sideslip angle buildup. You can easily go past the optimum sideslip and still control it. At this point it seems like you have to hit that peak to be fast, but the car is easier to control at and over the peak limit. Last edited by Jack B; 20 January 10 at 19:17.

20 January 10, 18:59	#2
~~Empty Box~~ Banned Join Date: Jan 2007	I heard about this before I left and it seemed very interesting. I've always noticed that you needed to hold the pedal at about 75% throttle to maintain (just maintain) speed. Which, would make normal street cars funny on the highway (Take that eco nerds!) So is this just an update or is it the end of season week 13 next season build?

20 January 10, 21:26	#4
AllanGP Donated Join Date: Jan 2009 Location: Wrexham, North Wales, 25 mins from Oulton Park Age: 51	Well after a week at Lime Rock just blew away my previous best lap at Laguna in the Slowstice by 0.6 sec in just 30mins getting used to the car there again. More front end grip, better feed back, nice one!! Allan

21 January 10, 09:31	#6
merlin Join Date: Nov 2006 Age: 38	not sure if they got the transmission model changes in to this build.but personally i love the consictancy of the newish tires on the skippy, upto yesterday i could not get around mosport incident free then after the change first race started 14th finished 4th amazing what you can get by just plugging away at your own speed

21 January 10, 13:05	#7
AllanGP Donated Join Date: Jan 2009 Location: Wrexham, North Wales, 25 mins from Oulton Park Age: 51	Should have said before - off road excursions (in the Solstice at Laguna) - of which I have many - seem a lot more controllable as well. Plus sensation when driving in gravel seems more realistic?? Now 0.7 quicker and not really strung a proper lap together yet. Also I like the way the nose moves up as you set off from standstill and the down change "blip" is better and more audible. Plus I got the option to re-calibrate my G25 so feedback is better with no issues as stated above. Allan

21 January 10, 21:40	#8
Mahjik Join Date: Dec 2006 Location: Kansas City, MO	I ran several laps last night at Daytona with the C6R. The good: I'm about 1.5 seconds faster with the update. The bad: so is everyone else. The lower end power is now trickier to put down on the Vette. TBH, this is closer to how I though the Vette was going to be when it was initially released. As mentioned, the throttle blips now are much lower compared to what was needed before. I'm still trying to decide if that's a good thing or not. I didn't really notice much else with the handling, but the car still feels good.

21 January 10, 21:58	#9
~~Empty Box~~ Banned Join Date: Jan 2007	Woa. First off - I like the fact that no longer do I feel like I'm almost full throttle to maintain speed. That's good. But, UMMMMmmmm...... Mazda? I can't drive the thing now!

22 January 10, 01:47	#10
~~Jack B~~ Banned Join Date: May 2008 Age: 55	Grant Reeve from iRacing decided to post and explain a bit more about the new iRacing Throttle Curve... If you ever wonder if all sims are created equal, they aren't. And even the simpliest things can get pretty complex. Here is Grant's explanation of the old and new throttle curves. Not sure what Mario Kart uses, but it's probably not this... ============================= The old throttle response curve was a simple y = x^2, which was done like a million billion years ago, way before I ever arrived at Papyrus in 98 and no one has ever thought to go back and look at it. We would know for all those cars we've modelled for the last 15-20 years what the full throttle dyno curve looks like, and what the off throttle engine braking looks like, but how the engine responds in between those two extremes I guess was never realized to be quite an important driving characteristic. I believe the original logic was that y=x^2 approximates the shape of a 1-cosine curve from 0 to 90 degrees which was supposed to vaguely model the opening of the butterfly valve in the throttle body (but in my mind I'd expect that the butterfly valve opening would be better modelled with a sine curve than 1-cosine, and that would have been a far better match to the actual response) The new throttle response curves are based on several sets of real vehicle data. One of the cars we model even has dyno information for full rpm pulls at every 10% of throttle position. By comparing how the engine power at any given rpm varies with throttle application I came up with an approximating function that sort of looks like the average of all the data we have. At very small throttle openings, the airflow is pretty much choked to a fixed amount, so regardless of engine rpm it's only getting a fixed amount of air to burn for power output. Thus the initial (first 10-15% or so) throttle response regardless of rpm is kind of proportional to power output. But at full throttle, the power output is limited by how much air the engine can pump. At low rpms the engine can't flow much air so it very quickly saturates it's power output, which is why at low rpm you feel like you're getting 80-90% of engine power by 40-50% of throttle, and the rest of the throttle travel feels very unresponsive. But at high rpm the motor can pump a whole lot of air, so the power output keeps increasing the further you get into the throttle. Eventually you start running into limitations of how much air the throttle body can flow when wide open, and into limitations of the engine's volumetric efficiency at pumping air at very high rpm, which causes the throttle response to still flatten off as you get towards 80-90% even at max rpm. It's quite likely that every engine in existance has subtley difference throttle response based on various build characteristics, but we're just giving them all the same response curve for now based on what their rev limit is. First time I tried the new curves - like most of you guys have noticed - it immediately felt incredibly more natural - even the Spec Racer (which I like to call a Death Trap) was suddenly a whole lot more controllable and drivable. So, yeah, it does seem that it's pretty important to model what happens in between 0% and 100% ================ So there you go. When iRacing decides to work on something they don't kid around. Can't wait to see how the new Transmission Modeling works out...

22 January 10, 01:54	#11
~~Roush9~~ Banned Join Date: Aug 2007	I've only tried the ImpA, but it felt exactly the same to me. Might do some Vette tonight to see if I can notice anything.

22 January 10, 20:26	#13
~~Empty Box~~ Banned Join Date: Jan 2007	I will admit. I looped the Mazda. I had NEVER done that before the other day. It actually feels like it has some power - it's more sensitive. I honestly feel like the throttle sensitivity has been jacked through the roof, but looking at the bars show it isn't. It's nice. I don't think it'll make to big of a difference on the Oval cars though seeing how your not on and off the throttle near as much. Plus you can actually stab the gas to get it to turn a little bit finally.

26 January 10, 16:50	#14
marc1111 Join Date: Jan 2010	Thanks for posting that Jack B. I missed that in the forums - great info! Yet another example of the thinking that iRacing puts into the minor but important details of their sim. My reaction to the throttle response now is that it is absolutely fantastic and feels much more realistic. The cars are much more responsive throughout the powerband and you really have to modulate the throttle more precisely at lower ranges of throttle application. It's great!! I've also noticed that I now use VERY little throttle while braking compared to what I did before. The car responds the way you think it should if you apply 25% throttle, ie it pushes!!!. I suspect this may have squashed throttle-while-braking debate that has bothered many iRacers (including me) since the sim was released.