Stock non-seq hesitation at 3500-4000rpm
 

Hello-

My car is bone stock, and boost patterns are very nice and very happy. But...

I understand that the factory ECU doesn't drop back into sequential mode after a high rpm run unless you go below 3000rpm. This is a big annoyance to me... every time I go carve up the twisties in the hills I'll hit a straightaway in 2nd, go to 60-65mph, then brake to ~35mph (3500rpm or so), turn, and have no power to leave the turn! I look over at the boost gauge, and it is rising, but in 2nd, it takes until ~4500rpm to get my boost back... that's a lot of lag time!

Is that much lag time 100% normal? If no, what should it be like? If yes, is there something simple to do to force the ECU to go back into sequential mode?

(BTW, as a sidenote, if that much lag is what going non-sequential buys you with a bone stock engine, then I don't forsee myself ever going that way :-).

Thanks!

Take care,
Shad

The PFC behaves the way you describe. The stock ecu does too but I don't know the rpm points. Maybe they are the same.

In any case, if you really want to accelerate hard again, yes, you will need to downshift back to 2nd. Your boost response would be much better if you at least had a downpipe on the car. A downpipe is a necessary mod for these cars IMO, even if you want to keep the car stock. It will decrease spool time, reduce engine bay heat, save over 20 lbs, and is safe for the car and will also still pass smog.

Rynberg is 100 pct right. Its a PIA, sometimes I'd like to stay in the 4000 RPM range, but if I want to boost fast I have to drop back to 3000 RPM to do it.

Hello-

Thanks for the responses.

Yah... it's kind of a PIA feature. The only reason I can guess why they did it is because the semi-primitive open-loop boost control could go funky otherwise. And, of course, in 1st gear, you rip by the 3500-4500rpm band quick as can be anyway, and in tall gears the lag doesn't matter as much to your net acceleration. The problem is that I'm in 2nd gear going uphill! Ah, well.

Regarding the DP, I know they help airflow quite a bit, but I don't want one. Anything that's a major help to airflow downstream of the manifold pressure sensor is a change that goes unnoticed by the ECU. As a result, my engine will have MORE air crammed into the combustion chamber (10psi of boost gives more air with less restriction), but no change in fuel. It goes leaner...

I know that people *say* that an ECU remapping isn't needed with that little (some "rule of 3" or whatever), but c'mon... that makes no sense. Something can't simultaneously radically reduce restriction AND not notably effect A/F ratios :-).

The thing is... I really want a stock car... I don't want a modified machine. BTDT... love it, but this one I'm leaving alone :-).

If anyone knows of some convenient "tricks" to play to force it back into sequential mode, that's groovy. Otherwise, I'll just have to deal with it. <sigh>

Take care,
Shad

You'll just have to deal with it.

And your concerns regarding a downpipe are completely unfounded. It is much better for the car to run a downpipe. It is completely safe with the stock ecu. Wade and many others, including myself, have done wideband o2 testing of the A/F ratios with the stock ecu -- it is still pig-rich, even after several bolt-ons.

You can ask any experienced FD mechanic/tuner in the country. You won't find a single one who wouldn't recommend a downpipe. The turbos will last longer, the main cat will last longer, your engine will run cooler (and therefore last longer).