J1NX3D

The D prod cars Ideola is emulating were an n/a running turbo head with high compression and carbs for approx 170-190 hp

morghen

The 924 NA is non-interFEARence.


You'd be shocked to find out otherwise..
Except the 924 NA all the others are more expensive to keep than the 944...

ideola

This setup is definitely interference, confirmed during assembly. No way to get the high compression and ideal quench without going interference, especially with the approach I took with this build. To refresh everyone's memory, I am using off-the-shelf rods and pistons for readily available sport compacts. The rod I am using has a smaller big end diameter and a longer center to center. The crank was offset ground to accommodate the smaller big end, with the net effect of increasing the stroke. The compression height of the pistons ended up being perfect for 11:1 CR, so the added stroke and rod length combined with CR should provide a really healthy bump in low-end grunt. Because I am using off the shelf components, it was not an option to have valve reliefs in the pistons. The goal was to come up with the least expensive way to build a high compression stroker. I was able to achieve that at about 60% the cost of my 2.2L stroker setup (as deployed in the Club Sport project).

As posted in other forums, here are more details and answers to some of the other questions posted about this build:

This motor is going into the D-Prod tribute car I acquired late last year (it used to belong to emoore924 and took a circuitous route thru FL before finding its way into my garage).

I am running a MegaCycle hard-faced cam with the Integral Stage1 profile, as I intend this car to be a fast-street cruiser. If / when I am able to get this on the dyno, I also have an original Integral Stage3 cam that I am planning to test out to see what differences there are between Stage1 and Stage3 in terms of power, torque, and curve. With the solid lifters, big valve head, heavy duty springs, and Stage1 cam, I would expect 7000 RPM to be no problem, although I do not intend to spend much time there.

The carbs are 45DCOE with properly sized Venturis set up for me by the factory techs at Redline-Weber. I don't have the build sheet handy, but they also included the low-idle bypass and a jetting / tuning kit that should allow me to dial in a very streetable configuration while still enjoying the power and torque advantages of the larger carbs. We discussed this at length during specification, and the Redline-Weber guy convinced me not to go with the smaller 40DCOE setup. He said he built many of these for the D-Prod program back in the day. The reason they sell the 40DCOE as a bolt-on kit is because it is more idiot proof, but a tradeoff in terms of power. The myth that the 45s are not streetable is due to the fact that most tuners back in the day did not use the low idle bypass on the race cars. Proper jetting and venturi are the key. At least that was what he sold me on, we shall see!!!

The trigger wheel is there to allow me to run a programmable ignition. Obviously, no need for EFI. My intent is to start the motor with the stock 1978 ignition system (mechanical dizzy and CD-based ignition) just to eliminate a variable, as I have no experience starting a fresh motor on carbs. My focus will be to get an initial streetable tune with the carbs, and then do the programmable ignition conversion thereafter. I am planning to use MegaJolt with EDIS, as this is the most affordable and easily attainable programmable ignition. It will allow me to test and debug the trigger wheel, VR sensor mount, and EDIS setup, which will pay dividends later as I continue to work on a complete EFI conversion kit.

I will be disappointed if I don't achieve at least 150BHP with this setup as-is, but I am hopeful with tuning to achieve 160BHP or better. My research indicates that the full-on race D-Prods were in the 180-190BHP range, but that was running on the ragged edge with open headers, 13:1 compression, race fuel, and Stage3+ cams. I am not going to race this car, or even track it. It is intended to be a show car and a fast-street cruiser. So if I can get stock 931-like power with a flat torque curve, I will be exceedingly happy.

michaelmount123

Nice job on your 'tribute' engine, Ideola! I built and maintained two of these engines years ago for PCA racing in GT5. Both engines went into real D/P cars, which were wonderful platforms; dominated GT5 wherever they ran for quite a while. Anyway, the original D/P engines were limited to 45mm carbs and made just under 200hp at the flywheel. The original engines I did were also 2L, but with bigger carbs and a more modern approach. They made 205hp. I then stroked them (like Ideola) to get to the 2.2L GT5 limit (at the time) and was able to make 235hp. This was in strictly race trim with very high compression, good 931 heads, 48mm carbs, dry sump, 8000rpm, etc., etc.

An interesting side note: When running these cars, a number of people who were involved with the original '80's era cars would come into our paddock and chat. I often heard that the engines back then were 'hand grenades'. I found them to be quite reliable, one surviving significant abuse by it's owner/driver (RIP).