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-   -   roll-on versus stomp-on throttle (http://legacygt.com/forums/showthread.php?t=9492)

Beanboy 03-06-2005 09:17 PM

roll-on versus stomp-on throttle
 
Yes, I can't wait to re-map and elimate the stutter. But what the hell is the deal with the huge difference between the open and realtime maps? Stomp on the throttle in third around 40 and first there is hesitation and finally movement, and it doesn't feel all that strong. Roll on the throttle very quickly and the car feels so much better.

I know it has been discussed before, just was out for a drive today and was testing it out. Wheel/housing size issues? Very annoying. Well, not that annoying, but jeeze. If Subaru is going to give us a delay with the electronic throttle, why couldn't they give a little throttle ramp-up automatically when you stomp on the throttle? End up with better response in the end...

-B

Hatt Marrington 03-07-2005 04:42 AM

I think it has more to do with turbo response than the throttle response.

*Jedimaster* 03-07-2005 08:05 AM

It's definitely a Suby thing. I kind of miss having a V8 and stomping the throttle and just moving out instead of having to finess the pedal with the turbo Suby.

Beanboy 03-07-2005 10:11 AM

Turbo response explains down low, but through the RPM range, stomping on the throttle just feels like it is produces less power through the rev range. Rolling-on the throttle just feels faster even when you quickly get the pedal to the floor. Some timing issue when switching from feedback to open maps maybe?

-B

*Jedimaster* 03-07-2005 10:26 AM

Yeah, I'm with you on that- it was the same with my WRX. It just isn't as responsive as a larger engine.

John M 03-07-2005 11:02 AM

My theory is that it has to do with their variable-voltage fuel pump system. If you just "mash it", the pressure isn't increased quickly enough to keep up with demand.

I'll be bypassing this "feature" as soon as I get the time to try it.

axis008 03-07-2005 07:26 PM

I thought it had to do with turbo spool, but I'm probably wrong.

Mach V Dan 03-07-2005 07:29 PM

It's turbo spool. Stomp on it when exhaust gas is plentiful, say above 3500 rpm, and you get power FAST. But stomp on it when you're down below 2000, say, and you have to wait, wait, wait for the turbo to spin up. If you roll on the throttle, the turbo can spool as you sqeeze on the gas, and it feels like there's less waiting.

Really, if you haven't driven other turbo cars, the Legacy has GREAT turbo response. Even a stock WRX has MUCH more turbo lag than this car.

--Dan
Mach V
FastWRX.com

axis008 03-07-2005 07:54 PM

Ok, I'm right. :p Thanks Dan!

LEGA-C-YA 03-07-2005 08:27 PM

Dan is right on the money here. As long as you pre-spool the turbo you will always get the car to leap forward when you bury the pedal

rossodave 03-07-2005 08:33 PM

Another thing to consider is the fuel map. On my MY01 Impreza the computer used a different map for WOT compared to any other position. If I remember right the map for any other position was slowly learned by the computer but the WOT was pre programmed from the factory and didn't change. I have noticed that the power seems less at WOT than with it almost wide open. Just my opinion and I could be way off....

Dave

*Jedimaster* 03-08-2005 05:01 AM

Dan, thanks for trying but this is an ECU issue. Even with boost ready to go, you still don't get the same power at 100% throttle as you do with 90%.

graff48 03-08-2005 05:37 AM

I also notice greater performance from the "roll-on". Kind of like having to ask nicely for more power.

CFar 03-08-2005 06:53 AM

Some of it is the electronic throttle, a lot more than everyone is giving it credit for.

There is a (relatively) huge delay between tapping the gas and engine response. Heel toeing and double clutching is a pain. My old WRX with direct link had no problem. You tap the gas the engine goes. Actually very little slack in the linkage.

Older M5's have electronic throttles that can actually be adjusted for sport mode if Im not mistaken. I suppose Subaru programmed the delay in (and made it less sensitive) to avoid people spinning and the like.

Unilat 03-08-2005 07:17 AM

Quote:

Originally Posted by CFar
Some of it is the electronic throttle, a lot more than everyone is giving it credit for.

Older M5's have electronic throttles that can actually be adjusted for sport mode if Im not mistaken. I suppose Subaru programmed the delay in (and made it less sensitive) to avoid people spinning and the like.

I don't have the link, but one of the ECU product vendors (I believe it was an ECUTEK vendor) stated that part of their remapping was in fact changing the mapping of the throttle by wire. I agree that this engine has a relatively sluggish response to throttle "blips", which I had previously associated with a heavy flywheel effect.

I have to keep telling myself that this isn't the old days!


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