Mrmerlin

We just rebuilt Matts intake today, we had a whole team out there it was almost like a champ car pitstop. I will add a few particulars the engine has about 75,000 miles on it, with the 32 valve 4 cam engine, the header pipes are rusted out, Matt has an X pipe to install, it has just had a timing belt/WP job done, and its a 5 speed, anyhow we started with with Rogers new fuel lines, a new set of injectors( 4 hole type), and it has the boxy intake ends and every flexible rubber line under and over the intake manifold,has been replaced. Upon startup the car cranked a few trimes till it built up fuel pressure then settled into a nice strong idle, as it warmed up we noticed that the throttle response was almost instantanious, almost like its an electric motor, just crack the throttle and the the engine screams, instantly.
Cracking the throttle on any one of the S4s present the engines all seemed to be very sluggish compared to Matts screamer, So the question? What gives? why does the 86.5 have such an instant throttle response?, And why doesnt the S4 do the same thing, is there anything that could be done to make the S4 have a similar throttle response, Thanks for your thoughts, Stan

PorKen

Plenum volume.

It could also be partly because the LH2.2 is not as 'self conscious' as the 2.3.

Mike Frye

And plus also, the early 32v engines ROCK!


Porken, nice wording, but they might want a little more on the technical aspects of 'self-conscious', no?

Mrmerlin

Please Ken do tell , does the bigger intake volume really let the engine accelerate that much faster or is the older LH system not as particular, more explaination would be appreciated, Thanks for your time, Stan and a few other interested S4 owners

Lizard928

the clutch is a smaller OD and therefor has less rotating mass where it matters, this allows for faster spool up time.

Garth S

Good question/observation. BTW, were they both 5-sp's?
Auto S4's are slow to rev for the additional reason that the primary vanes of the converter and prop shaft are added to act like a massive flywheel.
My early 16v revs almost like a formula engine in comparison to either the early 32v or S4 .... I had assumed that one reason was less resistance in the valve train drive.

Mrmerlin

Well we were checking S4`s with autos, (3 of them) so that might be some of it, ( drive line drag) but really Matts 5 speed car really just screams when the throttle is blipped, we were all (6 guys )amazed at the instantanious response, the S4 `s were sluggish by comparison, i guess we could have checked the GT that Fred had but he left before we could check his . the difference is night and day. the drive line added on drag makes sense, but with a 5 speed car the drive shaft is still turning and so is the main shaft with the clutch pedal released???? probaly less drag but???anyone else with any thoughts?

Garth S

True on the 5-sp if the clutch is released; however, after the stall speed of the autos convertor is reached ( ~ 1600rpm??), the whole flippin' thing - fluid & secondary vanes - locks up and spins in either park or neutral: now, that's a boat anchor..

bigs

Would it be informative to place both an A/T S4 and a manual 86.5 up on lifts - just enough to get their tires off the ground - put them both in gear, and then compare throttle responses?

Or do the same thing with both cars having the same types of transmissions...

leperboy

Yesterday was truly an amazing day for me, going from a car with sporadic problems to just a perfectly smooth, roaring beast. I think everyone in the garage had to give it a WOT goose a couple times. It was particularly satisfying for me to see all the guys with concours S4s drooling over the throttle response on my "corrosion-cours" gem.

I'll write more on what we did and why we did it, but a huge thanks to Stan for orchestrating the 6-7 of us to keep everyone busy, productive and do the whole job correctly in a single day (with time left over to start on the X-pipe job).

Thanks to Roger, too, for the fuel line kit and parts, and a recommendation to others to spend the extra $100 over refurbishment and just swap out your injectors for new Ford 4-holes. They are sweet.

Matt

Stan.Shaw@Excell.Net

Great to hear the car is coming along so nicely

I thought there wasn't any question the dual disk clutch of the S 928s resulted in quicker throttle response when compared to the S4 clutch.

Abby Normal

ABSOLUTELY!

mark kibort

ive had the S4 with the stock clutch and the 2 disc clutch. there is no "noticable " difference. However, scots 5 liter revs like a F1 car and mine is pretty sluggish as was said here. I think its an ECU difference. mixture, off throttle, spark advance, etc. throttle cable gearing maybe different as well, as the mechanisms are quite different between the S4, 85s and 2 valvers.

Mk

RDS928S

Matt,

wait until you install the x-pipe. Go for Dave Lomas' 100 cell high flow cats at the same time.
If you can swing it the 2.5 inch true dual exhaust will top of the whole project.
The 32v engines love to breathe.
Carl@ 928 Motorsports noted a 38 bhp gain on the 85/86 engine with the x and 2.5 inch dual exhaust.

Good Luck
Rich

IcemanG17

Interesting......I have noticed that OB's rev very quick too....or at least Gerry's 78 did until the cam broke

I thought it was the computers and more complicated throttle linkage that slowed the response.....intake volume...interesting...I wonder if anyone has done flow testing on the various intakes (OB, euro OB, 85-86.5 & S4+) my guess is the euro OB or 32V S3 flow the most in stock form....