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luvmy911

Can you help me figure out the lag from start up in 1st gear?

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Hello all - This is my first post here! Excoted to be a part of the fun here too!

I have a thread over at Rennlist and thought I might see if anyone here could help? Here is the link to the thread there but below is my result and on going concern:

2003 C4S 996

52k miles

Manual

Aftermarket Super Charger by TPC

If you re-read the OP, you can see the issues I was facing and I would say most are resolved....but not my main complaint.

1) Smoke Test found three vacuum leaks

Evaporative Line fitting on Intake Manifold

Re-seal the additional Fuel Injector (for Super Charger)

Re-seal Intercooler to Intake Manifold

2) MAF Replacement

Voltage was showing low and volume of air was not as expected at idle.

The MAF replacement alone yielded most of the improvement to the idle and startup. The inital "clunk" on start up is much less and almost gone. Though I will say it didnt resolve all the issues I see on starts from 1st gear. More on that later, below.

3) Pre-emptive replacement of IMS bearing with LN IMS retrofit.

I have the old bearing and it looks solid still. I would say there is a little bit of play in the bearing but only after it was uninstalled. My Indy said there was definitely a decent oil leak coming directly from the bearing (housing) so perhaps this was a good call on the replacement.

4) New RMS seal, of course.

5) New Clutch (kit)

was only 20% left on clutch so we replaced this too. What a difference! The clutch is very easy to push down now! Grabs much better now.

6) Transmission mount was shot - replaced

7) The rear Flex Disc was dry-rotted and cracked. Replaced.

8) New AOS

I have the old one. Seems to be fine but again, peace of mind on a preemptive fix.

9) Semi-Solid Engine Mounts

Make: RSS Tarmac

10) New Plugs (NGK BKR Platinum)

11) Fresh oil and filter (Indy recommended 5w 40 Castrol Syntec)

12) PA State safety and emissions inspection

So - Now I have peace of mind about some of the major issues that are possible with my P-Car. Most of the clunks are gone due to the 10+ hours of additional labor to lower the engine and re-manipulate the Super Charger pipes and stuff so they are not rubbing on the interior engine bay.

However, my main complaint is still there - though seems to be improved, not resolved:

That is, my start from first gear - I am just not confident I am not going to stall the car. I feel I need to rev to 2500RPM to ensure I can get it moving.

I have been driving a clutched car for 25+ years so I don't think its me.

There seems to be a lag when I press on the gas enough that something just doesn't seem right still.

Any other thoughts? I dont expect a perfect car by any stretch but after this monster bill, I would have thought my #1 complaint could be resolved.

Please chime in. Thanks!

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Sad to hear of all the problems. Seems you have resolved the air delivery issues. Other than that then the two culprits would be spark and fuel. When were the coils last replaced? Is the mapping in ECU correctly adapting the injector duty cycle....

Edited by 987_RDC

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I have not checked coil packs. Would a durametric be able to diagnose that with out taking them out and using a multimeter?

As for the ECU mapping - Supposedly the the good folks at TPC have a remap they do with the install of the SuperCharger - but I have no way of knowing this - - or, would the Durametric tell me this too?

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Is the MAF in front of the supercharger or after? How is the bypass done? Vent to air or cycle back into the intake?

I found on my Novi 2k system (centrifigual supercharger) that draw through MAF with the blow-off air vented back into the inlet (behind MAF) resulted in a very excellent street drivability. Same system later adapted to an atmosphere vent and blow throgh MAF was great for drag strip (high RPM launchs etc) but boggged badly in stop n go.

So it may very well be simply the design. Unless this was a sudden occurance.....

Edited by 987_RDC

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WOW - this is the most lucid set of questions I have had. On the other board, I am lambasted for my poor decision in purchase....

So - to answer the best I can -

The MAF is right after the coned air filter and prior to the TB.. The MAF is brand new (3 days old) and I have seen an improvement (50%) in response and start up immediately. I spoke with the manufacturer of the SC (TPC Racing) and they had several suggestions:

1) Unplug the MAF completely. Drive around the neighborhood a couple miles etc, and note any differences.

So there I stop, but are other suggestions from them are below. My inital notation is that the problem is FIXED! But with caveats.

a. The starts from 1st gear seem to be what I would expect. Smooth(er) pedal response, clutch engaged like any other car I have driven and I feel more confident about lower RPM engagement.

b. Right away, from start up I get CELs saying ABS and PSM failed. Expected some codes - no problem.

c. Car driving in neighborhood ok - starts from "stop" signs warrant what I would consider PERFECT clutch to ratio to throttle response.

d. 5 minutes in: idle is becoming an issue.

e. 8 minutes in: Lots of stange idle, low RPM thrusts.

Pull off road - shut engine off. 30 min later, reconnect MAF, small CEL and I am back to the regular behavior = my inital complaint.

SO....

TPC Supercharger tech told me a few things on this today - RE: the new MAF and a lack of throttle response.

*) He mentioned in later iterations of their design that they use a 2004 Audi S4 Throttle Body tube (with OEM Bosch 996 MAF).

*) That the "exact position" of said TB tube form S4 allowed a more specific and optimal "position" of the MAF, based on the SC/ MAF needs.

2) Restirct the airflow from the cone filter slightly. (Not yet attemted)

He mentioned that the 2004 Audi S4 TB intake had a "screen" in it. That was enough to restrict airlow to make the MAF happy. Thus, they started using it. Results were consistantly positive so this was an on-going-forward strategy.

3) Next, the two additional fuel injectors into the SC. He said to test them by pulling them out, turning the ignition on to see if there were leaks prior to starting. If so = fail and replace.

4) Lastly, He said there was a computer controlling the SC that could be failing. Really said that would be a ast resort and that the previous 3 would usually resolve things.

So, to answer your questions:

How is the bypass done? Vent to air or cycle back into the intake?

I actually am not sure about these answers. My SC company sadly stopped these units a couple years after the 996 was halted. If I were venturing guess, I would say "Vent to air". I say this because of the Hiss I get between shifts.

I hope this is enough info for you to weigh in more - thanks for your help.

Greg

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