Recently I acquired a ScanGauge II.

One of the things it shows in real-time is boost.

I checked the boost without my Unichip as I had it off for a few days doing some other testing.

With the Unichip not connected, the car produced 16.5 lbs of boost. But the part throttle applications felt lethargic compared to the Unichip.

FWIW - the car has Alta CAI, 15% pulley, 2% crank pulley, M7 intake runners, M7/Cosworth head, Schrick cam, Milltek, etc...

I put the Unichip back in, and checked the boost, figuring it would climb quicker with the Unichip installed. And it does, until about 9-10 lbs. of boost and that's it. Never gets above about 10, full throttle any gear. And when it gets to 10, it drops back almost immediately to 9 or less, as if timing or something is being retarded.

Go back to stock ECU, and the boost is back.

Question is, how the heck can something electronic cause the boost to drop 6-7 lbs./sq. in.?

The last dyno tune for the Unichip produced 207 whp, but the afr scared me so so we added some fuel. Dropped 10-12 whp. Added some timing and got 5-6 whp back.

Also, I just checked the summer tune (Map 2, from last summer, no timing changes, and a bit leaner overall) on the Unichip.

Seemed to produce about one lb. less, maybe 8 lbs. max.

Back then, I didn't have the ScanGauge II to check boost.

So I'm wondering how this loss of boost with the Unichip can occur? I thought max boost was mostly a function of the induction system.

And I'm wondering how much stronger it could be on boost with the Unchip attached and not retarding the boost somehow...

Or if the Unichip could somehow be corrupting the info to the ScanGauge II...

 

Jim, as I was reading your post, this was going to by response as a plausible answer. The likes of Dr O would know much more on this topic though...

If indeed you were getting that much less boost, you would notice it. Do some timed runs, with and w/o if not sure...

 

Did it happen to be warmer or more humid? That will play a huge part in what you see for boost.

In the cold (45F) I see around 17-18psi. Right now with it being so hot and humid, I might break 13...

 

Sorry,

Wish you were right!

I should have been more clear.

I uninstalled, installed, uninstalled the Unichip within an hour or so today. Temps and humidity remained almost identical from 2:00 PM until 3:15 or so.

 

The Unichip is a piggy back unit right? Is it possible that it's tricking the ECU into thinking there is a different level of boost? Since you've using a scan tool and not a "real" pressure gauge you're getting a measurment of what that ECU thinks the PSI is.

It wasn't clear if you are seeing the proper performance gains (i.e. the car is faster, but showing less boost). Is are you saying that the Unichip isn't working, or just that you are getting less boost?

 

Yep, that was the last thing I wrote in the first post.

It could be that it's producing full boost and tricking the ecu. Don't know if the info would be changed to the OBDII port where the ScanGauge is connected, or if the ScanGauge reads pre Unichip info at the OBDII port.

It definitely pulls stronger up to the indicated "9 lb." point. Trouble is, I tried to run the test on Christmas Eve afternoon with the traffic everywhere.

It doesn't feel appreciably weaker, but I find myself comparing 9 lbs w/Unichip to 9 lbs stock...

I'll try some timed runs this week, as Tony suggested..

And if the Unichip corrupts that ScanGauge MAP info, what about everything else, such as TPS, water temp, revs, and more?