3.2 throtle response w double clutch and...

[911st]

I am still in the stage of getting used to my 85 Carrera. It has a great chip and a cat bypass.

Throttle response seems slow. Is this a characteristic of Motronic EFI.

It is not quite as slow as my 930 was and a lot slower than I remember my 911S MFI was.

When I blip the throttle for a double clutch down shift the motor seems slow to respond.

Also, if I am idle and I make a quick stab the throttle to say 50% the rpms seem to not come up and drop a half a second after I have done so.

At least that is the way it feels.

Another issue is that when the motor is cold when I run the rpms up a bit and let off, the motor wants to or dose die.

Not such a problem after warm but still seems like the motor is trying to catch its self.

Thank you for any help or info.

[PSportoVeloce]

a steve wong chip will improve the throttle response and bring many other benefits. i just installed mine yesterday and i'm quite surprised by what a difference it's made, although it introduced that almost dying thing to my car, which did not suffer from it before. seems like a motronic problem. my bmw of the same vintage (5/87), also with motronic does the same thing when it's cold (but actually dies sometimes, and much more likely when on a downhill...) but cleans up when warm.

[stlrj]

I always said, the easiest way to kill the performance on a Motronic is to set it rich.

[911st]

To clarify I am not talking about how much intial torque it get but how fast the motor responds to throttle.

SWis a great chip.

I have a custom chip comming that should lean up This area. I was at around 13+ /1. Maybe this will help.

[911st]

The dying reaction is almost like the idle control valve / air bypass or what ever it is called, has to open to catch the motor when the rpms drop.

Maybe that is what is happening. When cold the valve has to be open. Then with increase in rpms it goes back to neutral. When we drop the rpms, it has to reopen to catch the motor???

I will pay more attention to this when warm. I know it is better but I do not recall how much.

[KTL]

I have a SW custom chip for my '87 which has different cams and a Kennedy Alum pressure plate. The throttle response is still a bit slow but much improved over the stock chip, cams and clutch.

I've seen my car slowly evolve with changing stuff around, and I can say that the issue you describe was most prevalent in stock form. After adding a 911Chips chip with cat bypass, the condition improved a bit. Then the cams and LW clutch helped further. The rev-ability of the engine has noticeably changed with the clutch and cam change. But the throttle response is still a bit laggy.

Would I do the things I did (chip, cams, clutch, exhaust) again? Probably not the cams (unless as a complete matched upgrade) and clutch- neither have been great bang for the buck in my opinion. Chip and exhaust i'd do again for sure. There's reasonable bang for the buck there. My "custom" chip likely needs some tuning since it's a base chip that should be remapped following installation and dyno results. Haven't gotten around to that yet. So i'm probably screwing myself as we speak.........

[911st]

Kevin,

The shop I use just noted that a rich condition will add to throttle lag.

I to have a Custom SW chip w cat bypass. Just received a new burn w a leaner beginning. If it makes any difference I will report back.

Also went back on the O2 as I had a euro style burn.

K

[burgermeister]

Can someone explain why a rich condition would cause throttle lag? I always figured the reason carbs are so peppy is when the throttle is blipped, the accelerator pump dumps in gobs of fuel - and the accelerator pump seemed to prefer a rich cam over a lean cam on my old Deroit Iron toy car. Just trying to edumacate myself, I have little experience with EFI.

That said, I find my 3.2 to have terrific throttle response, but I guess it depends on one's comparison ... it's certainly faster than I can shift without upsetting the tranny. I do have to keep my foot on the throttle while double clutching, or else blip twice, to keep the RPMs where they belong.

[911st]

I do not know.

I suspect that you need just the right A/F and timing advance for a given motor to make for the fastest response.

(Reduceing reciprocating mass helps.)

With carbs the accel enrichment is adjustable, to much and they will bog, to lean and they will lean cough or just offer reduce performance.

Carrera's have the Throttle plate a distance from the injector. It could be that Carrera's are able to deliver fuel through the injectors before the air flow catches up.

I think part of our enrichment for acceleration is at the fuel pressure regulator.

When the manifold vac goes away the fuel pressure goes up for more fuel out the injectors.

I am just making this up, anyone know why?

I wish I had a wide band installed.

[911st]

My motor almost dose not react to a blip for a down shift.

[safe]

A wideband doesn't have to be very expensive.

[911st]

New and Improved!

Steve took some fuel out of my low end and I seem to have picked up a significant improvement in throttle response when I blip the throttle.

Also, I had a problem when I blipped the throttle my rpms would drop below idle a bunch and when cold would sometimes die.

It also took a bit of roughness out of my idle I think.

Problem solved.

This is my first impression and I do not have a very educated butt so take it with a grain of salt.

[Quicksilver]

If you ever need to drop the engine for another reason...

Get a lighter weight clutch/flywheel setup in there and it will really speed up the blip process.

[ccus944]

Try adjusting your idle speed control on your throttle body...On your '85, it should be a 7mm socket...It probably needs 1-2 turns counterclockwise...I had a similar experience, and after making this adjustment, cleaned up the situation...good luck! Cus

[911st]

I was running pretty rich at idle so I had the shop readjust my idle CO. They had to go full lean there already to try to get close to spec but still could not.

I do not know if there is much opertunity with the 3.2's to reduce weight at the flywheel. I assunm the presure plate housing is aloy already and there is not that much to the flywheel in the first place. But I could be wrong but doing so would kick me up a class.

[Nine9six]

Originally Posted by Quicksilver

If you ever need to drop the engine for another reason...

Get a lighter weight clutch/flywheel setup in there and it will really speed up the blip process.

+1 on what Wayne said regarding "blip" enhancement.

[safe]

Originally Posted by 911st

I do not know if there is much opertunity with the 3.2's to reduce weight at the flywheel. I assunm the presure plate housing is aloy already and there is not that much to the flywheel in the first place. But I could be wrong but doing so would kick me up a class.

If it's stock the pressure plate is steel and heavy.

[KTL]

The 915 steel clutch housing is not nearly the boat anchor that is the G50 housing. Still, I think the 915 alloy clutch is a no-brainer when replacing a clutch. It used to be a steal of a deal years ago- 915 Sachs alum. clutch kit was only $100 more than the steel. Now the prices on clutch kits are into the stratosphere!

[JeremyD]

Originally Posted by KTL

So i'm probably screwing myself as we speak.........

Too much information there my friend - both hands on the keyboard please

[911st]

For what it is worth,

I saw a Porsche clutch take out once that not only the clutch housing was alloy but the pressure disk its self was also Alloy. The Face looked to be coper coated then there was a harder thin veneer that came into contact with the clutch disk.

It was very, very, light.

Anyone know anything about such an item?