Throttle response

[sylvester]

Hi.. I have a 79 SC coupe.. my question is... what makes the throttle response so quick on these older 911s. its kinda quick like riding a motorcycle. just curious thank you very much.

[T77911S]

if it is CIS, the vacuum controlled WUR helps. its a fairly light car, manual trans which means a more solid link from engine to tranny, no smog crap.
CIS was not a great performance system by any means although it did come on very expensive cars

carbs have much better throttle response

JMO

[Tippy]

I've never heard of a quick throttle responsed CIS?!

[porschenut]

This is a joke, right? CIS has the worst throttle response of any 911 ever made. Even the EFI 3.2s have lousy response. Good response is only had with carbs or MFI on the longhood cars. Or carbs or ITBs if installed on a later car.

[Tremelune]

Independent throttle bodies.

Getting ITBs on a Porsche is usually done by stealing parts form larger motorcycle engines. Nobody has a plug-and-play kit for it, though it is being worked on:

The next big thing....3.0 EFI/ITB w/Rasant engine management

[DRACO A5OG]

Have to agree 3.2 stock is really doggy but with properly timed 964 cams and SWChip, It makes a vast improvement.

+1 on SC, light ( lighter than 3.2 for sure ) car so it will be quick

[Josh D]

Advancing the ignition timing on a CIS 911 definitely quickens the throttle response. It isn't all the CIS fault.

[Bill Douglas]

It's a particuarlly good year for a 911SC, that may explaine the thottle response being excellent.


regards, Bill 1979 911SC

[prschmn]

Could be this car has an Aluminum pressure plate-less rotating mass helps a lot. Any intake with the butterfly farther from the valve has inherently slower response-hence ITBs or carbs make a huge improvement. Increased ignition timing can help but at the risk of detonation.

[garment]

How does one know what the "correct" throttle response should be? I associate response RPMs/where in the power band the car is when accelerating (which I guess is just one variable).

[Tremelune]

It's not so much a correctness as it is that you want minimum latency between when the throttle moves and the engine is at the speed it will eventually reach for that throttle position. Well, I do. This is ignoring the downsides of lightweight flywheels etc, but...This is pretty close to ideal:

https://www.youtube.com/watch?v=XRXwWbo_mX0&t=59s

The only real value I'm aware of is during shifting, and most of these cars rev fast enough for the speed that you should be shifting at, so...

[914efi]

My CIS 911 3.0 has better response than my EFI 944...

911 has a lighter flywheel for sure, but the broad-brush maligning of CIS is incorrect in my opinion. Properly tuned it is quite good as the OP states.