Dyno and Chip it?

[fastbacker]

I just had my 964 engine rebuilt by a reputable shop. It's ready to pick up in long block form. The long block is pretty much stock aside from a set of Carillo rods, cams and hd valve springs. The engine's going to be used in a PRC GT-Limited car. The class calls for a stock 964 or 95 993 plastic intake and a 1 5/8 header. I'm using the 95 993 intake.

As a first step in learning about this engine, I'm going to install all the accessories on the long block - intake, exhaust, fan, distributors, etc. The shop who built the long block highly recommends I bring the engine back to them when it's finished so they can dyno and chip it. Their reason for this is to break it in properly and for the best possible chip (via Steve Wong).

My question is - to save money, can I order a chip without dyno charts (using my engine specs) and break it in myself. I realize the chip won't be 100% but won't it be within a hp or two? And, how hard is it to break in an engine properly? Or, is a dyno run that valuable for potential problems?

Thanks-
Craig

[Steve@Rennsport]

Craig,

I would strongly suggest that you follow your shop's advice,.....

Let them break-in the engine properly and furnish AFR data to Mr. Wong so he can do the job that you expect and deserve.

You would be quite surprised at the differences.

[fastbacker]

That's all the advice I need. Thanks Steve.

[s5uewf]

I used a series of dyno runs and sent the data to Steve Wong so he could in turn adjust my chip settings and send a new updated chip (I return the old chip).

Running on the dyno and getting Air/Fuel data across the RPM range is invaluable in tuning the engien while ensuring it is still getting enough fuel to avoid detonation.

[Steve W]

Craig:

Having mapped several of these race PRC 3.6 motors for engine builders, it is absolutely critical to have the chip custom mapped and tuned if you want to be competitive. Your shop is probably speaking from experience as we've found no two of these engines to map even remotely close to each other. Properly mapped, and depending on fuel, these engines will put out 315-320 hp on an engine dyno, and measure basically within 1-2% (dare I say are actually faster) than the same engine with the entire Motronic system replaced with a full Motec engine management system.