We put a forged bottom end, cam and LT4 (ported) blower on a Camaro SS. Car starts and idles great but the MAP is reading around 80kpa at idle. Seems high. As soon as you start driving it the car starts bucking and pulling timing. The fuel trims start pulling tons of fuel and the car becomes undrivable. You can see in the scan that the map spikes when the timing drops
Are you running LT4 adapter plates to bolt it to the cylinder head? They usually leak vacuum and cause this issue due to the bolts being too long
Agreed, car was smoke tested already. No vacuum leaks though. That is my first go to
Smoke test won?t always tell you if you have a Vac leak? it?s a great tool, but it surprises me how many people install the lt4 supercharger wrong and can make an ?internal? vac leak sometimes with crankcase pressures so a smoke test won?t tell ya
Depending on cam size (but unless it?s upper 23x duration on the intake) you have a vac leak
The cam is a BTR stage 2 boosted cam and they don't have the specs. My other concern is that we're running an LSA 3 bar map sensor. The offset on those is -11.25 but we're only allowed to go as low as -.1
Can that cause any issues?
Also, we've installed a bunch of LT4 blowers now on LT1 cars. Haven't ran into any issues like this before. The bypass valve is routed correctly. What else would cause an internal vacuum leak?
You can 100% make the offset -11.25
That cam will idle around 60kpa at 750
Injector seals or the lt1-4 adapters.Originally Posted by JASON11WS6
Pretty sure injector seals would fail a smoke test. The adapter plates would for sure
You'd think so, but you've got a vac leak somewhere I'd think. Is the bypass functioning properly?
I’ve seen swaps where the hole under the blower is routed incorrectly which makes for a decent size vac leak..
Email Tunes, [email protected]
96 TA Blown/Stroked, 4L80E/Fab 9
15 C7 A8 H/C 2.3 Blower/PI
14 Gen 5 Viper
Custom Mid Engine chassis, AKA GalBen C
Funny, in the end of your log at idle (550 rpm) your BARO is 98 kpa and MAP is 106 kpa... and Fuel Rail Pressure is 14000 kpa btw.
Vacuum leak somewhere or incorrect routing, definitely.
If you don't have an LT4 valley cover the hole on the blower will leak yes. We have an LT4 valley cover and we even took the blower off to make sure it was seating properly. Everything is good to go there, put the blower back on and same old story.
I tried to put the true value of the LSA map sensor in the since the offset wasn't matching. I entered -11.25 even though hp said it was beyond the limits.....the car wouldn't even start. I entered the lowest number it would allow and it started back up with the same issues.
We tossed the stock map sensor back in and it seems to be running fine. Except if I gas the throttle a little bit. It'll rev up fine but when it's coming down the kpa goes up for a second the timing plummets for a bit (car sounds awful) and then it steadies out right away. I'm going to try and drive it around a little bit tomorrow like this. The thing that pisses me off is I tried two different lsa map sensors and they both acted the same way. I've used them in plenty of other boosted cars and even on another 2019 Camaro SS. Same car, same blower upgrade but never had an issue with the map. Changed out the bypass valve to make sure that wasn't the issue and it does the same thing...maybe a bit better though.
Here is the last scan. You can see it gets stuffed up for a second but smooths out.
Reply With Quote