rixter

suffice to say I have totally screwed up the design on this engine project, I got the main items backwards and need help getting this back on track before I start the build (I managed to catch my mistake PRIOR to starting thankfully)

goal: 500+ rwhp, low compression engine (8:1) with high boost (15lbs)
I do not plan on tracking the car as the extensive bodywork I'm planning would be a nightmare to redo, I do want to be able to dial up the boost as needed to match anything I come across in my travels, it will NOT be a daily driver

I had planned a 5l 85 block w/Euro S top end, I got my measurements all backwards and looks like I'd be looking at 11:1 compression which just won't work with massive boost

so, I guess what I really need is help in getting a good, driveable low compression engine designed... money IS an issue, I know custom work needs to be done, but I'd like to keep it to a minimum... I DO have access to most of the main engine components

I plan on using DR's SC for the boost, so any design will need to accept this

any suggestions?

FlyingDog

85/86 engine with S4 pistons should get you into the 8s for CR. You could do a Euro S engine with 83-84 US pistons which should also put you in the 8s for CR. If you want to really turn up the boost, custom pistons would probably be a good idea.

jebdog

The S-4 pistons with Euro two valve heads should get you pretty close on compression at the least cost. What engine management ,injection do you plan to use ?

rixter

thanks guys
I'd honestly like to use CIS, I knew all along I'd probably have to have the pistons either custom made or altered which I'm ok with

Mongo

a very thick head gasket and S4 heads

FlyingDog

How are you going to use CIS with DR's TS kit? Where will the air plate, fuel distributor, and all the other necessary parts go? Using an electronic system will make your life much easier.

Jim_H

Will DR's kit get you 15lbs of boost?? Is there something in the works we don't know about? A custom crank pulley?

SharkSkin

DR is working on more than one kit.

rixter

Matt, I'd like to use CIS but not totally committed to it
JimH, not sure if it'll give me 15, but DR could probably get me there if I really need it
I know nothing about any current plans/designs he's working on, guess I should check to see if this amount of boost might be possible down the road
I'm in no hurry to finish this project, it's a long term deal, just want to do it right the 1st time and not have to scrap everything and start over at a later time
guess I'll go with the 85-86 w/ S4 pistons, both are available without too much cost
now... what to do with the EuroS cams and throttle body I bought?

tammons

Forget using CIS. I have been down that road. You could do what I did. CIS, haltech, then finally tec like was recommended in the first place.

I ran a couple of days at 12-14 psi in an early TT 5 speed and it was wicked fast. It was so fast it would beat me though the gears. I was running custom T3 turbos. Basically 2 SVO turbos, with work. You definitely want a later longer 5 speed gear box. Also it was very difficult to drive in the rain. I ended up backing off to 8 and leaving it there.

I am not saying CIS wont work. With a lot of tuning and new parts you might be able to run it up to 10 psi, but anything beyond 10 starts getting critical.

If you blow through and dupe a 930 CIS setup you might have some luck. At least I think a 930 is blow through if i remember right. The most critical of all at 15 psi is timing which you have no real control over unless you use an msd box and that is sort of crude compared to EFI with spark control. You also might be able to boost the fuel with a vortech rising rate FP reg custom tuned.

At high boost some fuel is used to cool the charge, so you are running pretty rich, but you dont want to run that rich all the time. Maybe just gradually up from 6-8 psi and up.

I would suggest a Tec III. I ran a tec III for a couple of years and it is expensive, but well worth it. Once you get used to them, it takes about 2 minutes to get the engine started, and in about 1-2 hours you should be close with programing. Install is about a day, but not that bad once you get everything together.

Very easy to program, and the latest tecIII has a data feedback loop. IE do a data log run, with your wideband O2 #'s set as you want them, stop do a feedback and it changes the fuel tables to match.

Total engine control no matter what brand is the way to go, but avoid the earlier Tec II's.

The hardest part is machining the HB to mount the trigger wheel, and fabing a clamp for the pickup. My machine shop charged me $120 for the HB and the clamp is very simple.

Also the tec II is very touchy around what i call poking around speeds just off idle. It takes some fiddling to get it right in that area.

I am still wondering, why nobody has setup a megasquirt plug and play on a 928 yet. I think there are a couple of guys running MS on the 951 forum. With the cost of rebuilt computers, it seems like it would be a good option.

MarkRobinson

Buy my '85/86 engine (disassembled), for $900, put S4 pistons in it for a few hundred (more), & run a Tec 3 or so per Troy (above). Or, I'll be making a harness adapter for the '85-86 cars to run AEM & can hook you up with that as well.

My power is adjustable from 385rwhp on up, just switch the boost button you want. With the superchargers, you'll have to change the pulleys & ensure your belt can still grip the pulley to increase the boost.

Shane

So where can a guy get a set of "forged" S4 pistons at a reasonable price?

MarkRobinson

You can't. You can buy Forged GTS pistons for about $400 each, or 944 turbo pistons new/used, but need rod-lengthing/deck-shortening to run them. GTS & 951 pistons are the only forged Mahle 100mm bore pistons out there.

This is why I don't want to run S4 pistons: I don't want to be pushing the envelope on a stock cast piston.

Shane

I looked at both of those options and neither are attractive. Lag & associates I believe at one time had a group buy on some forged S4 pistons from Mahle, that I opted in on, but I never heard back from them. They needed five sets ordered I "think".

Jim_H

I am needing to check in with him also to see what is in the works.

The TS is an excellent way to go. I just got my second one hooked up last week end and forgot what a change it makes. Instant throttle response and linear power. Very easy to install, not all the heat a Turbo adds, many proven systems being run etc.