Anyone know what the max PSI is for a GM TBI unit? I know there were some 454cid setups that ran around 20 PSI, but I’m curious how much higher they could go for 2 reasons – increasing flow rate of the injectors and also using a more-common MPI pump instead of a low-pressure TBI pump (limited choices).
1. These are side-feed injectors and from what I can see they might not have fuel ‘above’ the pintle, thereby fuel pressure would not be trying to keep it closed (like a typical Bosch-type injector) therefore leakage would only be a function of the TB gaskets. Can anyone confirm that?
2. My next question is about using a more-common high-pressure MPI pump with GM TBIs. I am concerned that the higher pump flow at the low pressure might overcome the internal FPR and cause a pressure rise at idle (and/or gasket leakage on the TB). I could remove the internal FPR and install an external one, but I’d rather avoid that expense unless I have to. Would an MPI pump flow too much fuel volume and overcome the regulator spring?
MPI pump with GM-TBI system, max PSI for TBI injectors?
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
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MPI pump with GM-TBI system, max PSI for TBI injectors?
Needs to get the toes out of the water and just jump off the diving board!!!
current EFI project:
65 Chrysler 300L, 413, working on inline dual GM TBI units, will run with MS2. Hoping to have factory-style appearance.
current EFI project:
65 Chrysler 300L, 413, working on inline dual GM TBI units, will run with MS2. Hoping to have factory-style appearance.
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Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
Re: MPI pump with GM-TBI system, max PSI for TBI injectors?
We've used a high pressure Walbro 255 pump with a stock GM TBI regulator and didn't have a problem. Not sure about where the injectors max out though.
Re: MPI pump with GM-TBI system, max PSI for TBI injectors?
Matt, I was hoping to hear from you, you always have good info! You'll be getting an MS2 order from me someday soon.
That's good news on the pump, that allows me to build for the future and do either TBI or MPI without a pump swap.
That's good news on the pump, that allows me to build for the future and do either TBI or MPI without a pump swap.
Needs to get the toes out of the water and just jump off the diving board!!!
current EFI project:
65 Chrysler 300L, 413, working on inline dual GM TBI units, will run with MS2. Hoping to have factory-style appearance.
current EFI project:
65 Chrysler 300L, 413, working on inline dual GM TBI units, will run with MS2. Hoping to have factory-style appearance.
-
Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
Re: MPI pump with GM-TBI system, max PSI for TBI injectors?
Yep, that was the idea with the Nova, two different fuel setups without replumbing the whole car.