tuning turbocharged ITBs? anyone?

tony2ltr · Post by **tony2ltr** » Tue Jul 04, 2006 9:35 pm

I have a cosworth vega that I am running MSII and EDIS. This is a 4 cyl 2 liter. I have fitted a set of Jenvey ITBs from a YB cosworth engine.
Here is the trick This is for a turboed engine. I have made a plenum box with vstacks inside that hpefully will distribute air evenly at most RPM/Pressure, I have had some guidance making this from others on this forum, but does anybody have any tuning experience with this kind of setup?

ArttuH · Post by **ArttuH** » Thu Jul 06, 2006 5:53 am

I have that kind setup on my bike. I Megasquirted it couple of years ago used it two seasons normally aspirated. I installed a turbo during last winter and now it's running pretty nice.

I used speed density algorithm without any problems when the engine was NA. I was able to tune it just fine, also for idle. But with turbo I faced some problems. I tend to get way too high MAP values (like 100-110kPa) when cruising at steady speed and low throtle opening. I guess that the reason for this is increased exhaust backpressure combined with quite big overlap. Anyway, it made tuning very difficult, it was impossible to tune it for both cruising and acceleration.

So I switched to hybrid alpha-N and it seems to work much better. I haven't tuned it completely yet but at least I can tune it for all situations now. Only drawback is ignition control. It isn't so handy to define engine load by TPS values with turbo.

tony2ltr · Post by **tony2ltr** » Mon Jul 10, 2006 3:50 pm

Where is your MAP? is it in the runner side of the ITBs, or in the tubing from the turbo?
\
Tony

ArttuH · Post by **ArttuH** » Tue Jul 18, 2006 11:15 am

The MAP is connected to the runner side, between throttle plates and the engine. I think this gives better resolution for low throttle openings.

Fastest95PGT · Post by **Fastest95PGT** » Tue Jul 18, 2006 2:44 pm

ArttuH wrote:The MAP is connected to the runner side, between throttle plates and the engine. I think this gives better resolution for low throttle openings.

It had to be between the ITBs and the motor as you have it. Otherwise the motor would never read vacuum so you'd have a hard time driving it that way.

tony2ltr · Post by **tony2ltr** » Wed Jul 19, 2006 5:48 am

Right, I can't believe I asked that, that is what I get for posting at 2am.
I have drilled and tapped my runners for NPT fittings, and plan to run them to a common plenum that I am planning on using for both MAP and Vacuum boosted brakes???. My mistake is that I tapped the bottom of the runners, not realizing at the time that my secondary injectors are going to be shooting right at them, now I am worried about my common vacuum rail filling up with fuel.--Whoops!!! I just hope I have enough vacuum volume/speed to operate the brakes, because of the small holes in the 4 barb fittings (3/8) that are tapped into the runners.