BC

Useless? I may do this to break in an S4 engine in the body and electronics of an S3.

Otherwise, maybe the S4 complete engine with no flappy control while breaking in the engine with the 86 ecu.

atb

Brendan,

Doesn't the S3 block have extra bosses on the top of the block for the throttle body to bolt to?

mark kibort

why would you want to do this? flappy is only a lugging luxury for street driving. for racing, you never even see the range of rpms that are helped by fappy. But more of interest, why would you want the stock intake only for break in?

Mk

Rick Carter

I think you should do it and after the engine is broken in dyno it, then after putting a S4 intake on dyno it again. This is solely for selfiish reasons, I want to see the difference between a S3 and S4 intake on the same car.

BC

As I touched on in the post, the reasoning (if there is any) is that I may want to "break in" a motor (89) that I am assembling in the 86, and the easiest way to do that is to stuff it in the 86 and run it with THOSE electronics. The other option is to run it with megasquirt, but that would involve a new tune from scratch AND breaking the motor in.

The motor has been balanced with a flywheel I installed a custom timing ring on for the use of Megasquirt, but I guess I can just zero balance the original OEM flywheel? or is that not ideal?

BC

Ah, yes. That is a good idea.

Rick Carter

Will the 86 electronics work with a non 86 flywheel? IRRC the 85/86 has 2 missing teeth and the S4 has 1 missing tooth.

928SS

fwiw, I had to change my flywheel when I upgraded to S4/GT stuff from my OEM 85S stuff.... also as noted, there's a big chunk of metal in the way on the older blocks that has to be removed if using a later intake, TBody, airbox and heads.... also the harnesses, fuel plumbing, breather stuff and timing belt stuff needs to be appropriate for the MY heads and intake being used...

I can show you what happened/I had to do on mine to make it all work, if you want. it's not a trivial process by any means/but quite doable if determined.

and don't forget the earlier heads have different sized chambers than the later stuff too, so your compression may be wacked out if you aren't paying attention w/piston volumes

BC

It would be (if done) a 89 block through and through, heads as well, but just with an 86 intake.

But just as Mark K. said, the flappy is for power below 3500, so the car would still...run, I guess, if I had to put it in with the S4 intake.

The flywheels I have are all 86 or my custom one, so thats not a problem I think.

928SS

hmmmmm, sounds like more fun than dropping a trans on your foot iirc, fitting my original intake on the later heads was going to be more trouble than it was worth - the ports don't really line up very well either. might be a real PITA that would also make re-using the parts impossible once you start removing metal...

iirc, the later intake is good for about 25BHP or so on a stock 5L motor, and up to 40BHP on a modified (6.0 and up) motor... if you look at the specs btwn the GT and 85S, 288bhp vs 315bhp - the only real diff is the intake, ECUs, smaller injectors/larger valves and ports on the later cars... cams were a wash, electric fans vs mechanical on the OB's - but AFAIK, no other performance affecting mods. my guess is the valves/ports are good for 5-8bhp, fan maaaybe 1-2 chp, and the rest has to be intake design and tuning (later stuff had knock sensors, so we could run slightly more aggressive timing, iirc)

but if it can be done, I"m sure you're one that can make it happen, although it might have a hard time passing the sniff test/ smog depending on the mix of injectors, intake and ECU's... good news is that most inspectors wouldn't be able to tell the diff btween intakes if it says porch/or something close on them, so passing visual would probably be easy

SwayBar

I do not agree; the various 32v cams are significantly different from one another.

Rick Carter

Maybe, maybe not; no one that I know of has tested S3 and S4 intakes on the same engine. My 85 was putting down 291 rwhp NA I seriously considered putting a S4 intake on to get the "extra" hp but I couldn't find any hard evidence it would make a difference. Until some one actually does there is only conjecture.

BC

I may find that the 200,000 mile injector loom and sensor loom is unusuable anyway, and it will force my hand to the megasquirt ECU. I have learned my lesson, however, and anything I do involves having a working 928 to drive while i do this, or at least until the 85 sells, which is that car I am driving.

928SS

btween GT and 85/86, sorry.

actually, it's been done a long time ago. these motors are 20yrs old, and there isn't a lot of NA work that hasn't been tried by 2 or more HP pcar shops.

fwiw, I did a fair amount of research before I made the jump, cause it's a real can of worms once you opt for GT heads on an OB 32V motor some of my better sources included mark at devek, greg at precision, professor ott, the guys that build heads and motors for kelly moss (a 928 race team), and several others that have have done quite a bit of testing w/various 928 intakes and intake mods over the years..

their results also confirm the published specs on the 5.0L 32V motors, if you compare the motor changes vs performance btween various MY's. so it's kinda beyond guessing at this point, although it's not as widely published as cheby/ferd/moparts motors are...

but only some info is posted here, cause a lot of the research was done long before rennlist was a sputtering electron... I'm just passing it on as best I can (but the memories do fade a bit after a while)

hope this helps

ps. I learned my lesson too b! now I'm going to have to get a track car, cause my daily driver is too much hassle to keep taking apart! hahahaha