Hitting cut around 12 psi

[cartert]

I've got an 88 with 7m-gte. Mods are 60-1, 2.5" ic piping, divorced downpipe, 3" exhaust with apexi n1 muffler, 255 walbro, cone air filter, etc. I've gapped my plugs properly and double checked the timing. I was hitting cut around 11-12 psi, specifically in 3rd gear or above. Most times I can make it thru 1st and 2nd without hitting cut. To describe cut the engine hesitates briefly then picks back up. I drilled my stock maf and back the screw out a little further. Seemed to improve the cut issue a little bit. Is it normal to hit cut around 11-12? Any suggestions on what my next step should be?

 

[Nick Squire]

yes it is normal, our cars hit fuel cut at ~12 psi. If you've already put on a mhg and arp hardware then I'd look into the lexus afm and some 550cc injectors, do a search on the lexus afm 550cc mod, there are a couple write ups

 

[BrandonW]

im running the 57 trim but with 550 rc low imp injectors mostly running 15-16 psi but if its a cooler evening (summer is coming to an end) it has gone to 17

look into the 12v mod for your fuel pump I have that done, im also running a safc II

I was hitting fuel cut around 8-10 before fuel mods

I didn't mess with the lexus afm screw

 

[cartert]

I have done the 12v mod. I'll look into getting 550s, lexus afm, and safc next. Thanks for the helpful responses!

 

[MK3pizzadriver]

Also keep in mind that the more volume you add to your intake, intercooler, and exhaust, the less psi you are going to see for the same horsepower.

 

[Rollus]

Also keep in mind that the more volume you add to your intake, intercooler, and exhaust, the less psi you are going to see for the same horsepower.

I'm interested to understand why please?

 

[BrandonW]

ok yeah since you are still on the 440's and stock afm

 

[MK3pizzadriver]

I'm interested to understand why please?

Maybe one of the gurus can explain it better than I can, but I remember the same thing being told to me at some point. When the turbo is blowing the same max cfm in a 2" pipe as opposed to a 3" pipe, it's the same amount of air, but at a higher psi. It's not having to work as hard in a 3" pipe though, so you get better performance. That is unless the intake is too big for the turbo/engine. Then the turbo can't flow enough air to create substantial pressure. So you may lose some lower end performance for more air flow up top at a lower psi.

 

[Nick M]

I have done the 12v mod. I'll look into getting 550s, lexus afm, and safc next. Thanks for the helpful responses!

In the TCCS thread it is noted that the Lex (1UZFE) meter is actually 28% larger than the 7MGTE meter. Which is pretty close to the standard claim of 25%. That slows down the frequency from the airflow meter at the same volume, raising the fuel cut.