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Nitrous would probably help, but in that case I would have to have it constantly armed and probably go through it quickly. This even applies to 0-50% throttle snaps not just 0-100, in which case you shouldnt use nitrous anyway. Not really sure of another way to fix it if it is a airflow problem...any ideas?
I have a hard time believing 10psi after .4 seconds doesn't get those turbos moving enough to start liking it. Those are some big-ish turbos though. Aren't all the guys making 900 wheel on a single?
You don't have much room left, but you could put a filtered 1-1.5" pipe/bung in the blower intake tube, obviously only as a test. If it seems to light up more to your liking, then you can consider setting up a wastegate backwards. Thats probably the extra "complication" you talked about earlier. Clearly I'm no expert, but if theres a large amount of vacuum between the blower and turbos, you have to feed that blower more air.
I'll be patiently waiting for a pressure reading between the turbos and blower!
Well so there are 2 issues really; blower lag and transient fuel. The fueling I will eventually figure out, but the mechanical blower lag is the bigger issue. Here is the best way I know how to explain it:
The green box shows the transient fuel delay. This is basically a lean tip in that should be able to get fixed through tuning. I dont remember it being as bad as this so thats interesting. As soon as I touch the throttle it goes lean and the rpms even dip slightly before they pick up.
The yellow box shows how the boost curve slowly builds instead of more steady with constant throttle. Also notice the little plateau in the beginning which is interesting. Normally I would say belt slip, but I have an 8 rib system with HD tensioner so slip should be minimal.
Anyway, add these 2 together and throttle response aint so great :/
I could just remove the intake pipe and wastegate springs entirely to test blower response if its a short burst obviously, would risk overspeeding the turbos but could stuff a sock in the intercooler or something to prevent that.
At only 42% throttle, you think the plateau could just be turbo lag? What boost did the whipple only setup make at 42% throttle?
If it ends up being a inlet restriction due to the turbos, which your planned vacuum test will confirm, I had a similar idea as Shaggy above. However I am not sure how a diaphragm type valve work since you would have to reference the same vacuum you are trying to relieve. A mechanical spring pressure valve may work better in this application. Better yet a two way spring valve may also solve the overboost issue with the turbos without having to go to the 60mm wastegates..
Well I'm more looking at the shape of the curve than the total value, at 40% throttle it won't be full boost, but should be pretty steady. Yea I can think of a few complicated ways to let the blower breathe effectively but those may not be practical or attractive. I wouldn't want to just bleed boost on the inlet side, but I originally did have a just 60mm BOV installed as kind of a last chance pressure relief.
Nitrous would probably help, but in that case I would have to have it constantly armed and probably go through it quickly. This even applies to 0-50% throttle snaps not just 0-100, in which case you shouldnt use nitrous anyway. Not really sure of another way to fix it if it is a airflow problem...any ideas?
What would a larger pipe inlet to the blower do? Could reduce vacuum but may still be laggy? Unsure but seems better.
I currently have dual 3in to a single 4in which flows perfectly into the TB. I don't have room to fit anything larger and even if I could the difference in volume would not be much. See pic above.
06-19-2019, 09:41 PM
