Throttle response from 3K! Ouch!

[jaykay]

I did some testing with fellow forum member Heiko and his new 74mm throttle body. His car (same as mine 2000 S) is really quick and accelerates amazingly well! Well I now know what I have been missing with the 74mm. The time in his car really accentuated the throttle response issue that I am having.

In 3 or 4th gear at 3K it seems like it can take up to 3-5seconds to get over 4K! At 4.5K things wake up and seems fine but it is all too late! At 3K, I would look over at H and say I am “flat” (pedal to the floor board) here… and his reaction would usually be dismay…

Could my used TB be defective? Is there a vario-cam problem? Is there an intake or exhaust acoustic problem?

Heiko’s car is pretty much stock with the exception of the TB and intake plumbing for it. The plumbing is potentially “smoother”. His engine is better maintained..

Mine is modified much more:
short snorkel
rougher prototype intake tube for the 74mm TB; 3.25” dia. rather than 3”
secondary cat by-pass pipes
stock S by-pass muffler (worse flow?)
softronic tune
leaky spark plug tubes/older plugs
older air filter
5w40 oil….heavier

I am wondering if the stock tune works better with the characteristics of the 74mm TB. Any thoughts?

[Nine8Six]

To my knowledge, and that's almost NIL, when you do A/F mods to a motor you need to get the ecu custom remapped or you'll suffer in either low, mid, or high range (or all). Needs a dyno, a few runs and an experienced tuner able to read and remap A/F curves for your given set-up.

Just a guess mate

[jaykay]

Sure true..... A/F tuning on these cars is quite involved. The DME should be able to compensate for more air

The implication here is go back to stock in the same areas and see what happens. On the exhaust side this means more back pressure to boost scavenge velocity......put the 2nd cats back in....arrrrrrgh! Stock muffler!

Snork up the intake.....I am using a larger dia. intake duct than everyone else I know of...3.25". This would have to go down to three.

Stock tune...

I suppose if anything were amiss like an MAF sensor I would see codes.

Then start timing the changes in engine acceleration with a stop watch...or camera

[Hayden]

I'd start with the intake side of things, and check the MAF. It seems a more likely culprit than the exhaust tuning, which as I understand your setup to be, shouldn't cause a massive dead spot. There's a lot of flow dynamics in the intake path so that air hits the MAF in a way that is in accordance with the rest of the system. Turbulence/swirling could be a factor.

[jaykay]

You could be right. It might be that I need a snorkel back in to give me this. But it is so far down stream of the MAF and in front of the filter... That I wonder.

I have my own snorkel in there now ....here is a picture of it versus stock. It is a big difference!



It may be that my intake pipe is to turbulent.

[Bigsmoothlee]

If you are experiencing hesitation, replace you air flow meter. Its not your throttle body, and it isnt a modification you need.