I installed a Paxton sn92 on my wifes 91 z28 350 tpi car...The car is Speed density too... the blower was sent to paradise wheels for a rebuild and upgrade...I installed an AEM air fuel gauge idle is fine go into boost in goes lean...I already have a high flow 255 lph fuel pump installed,I have south bay fuel injection adjustable fuel pressure regulator I have it set to 52-55 psi I wanted it rich well its not the car has 22 lb injectors..how can I get more fuel to make the car rich under boost?....I have paxtons direction no mention of an FMU it does say reduce timing which I did...so any help would be great thanks.....

 

You need 24lb injectors..

 

Is the reg boost referenced?

http://www.injectordynamics.com/Stec...reArticle.html

 

The regulator is from south bay fuel injection...I adjusted the pressure with the Vac line off car was running i have it set to 52-55 psi....almost seems like its all the way down for the adjustment...really cant get more out of it...the fuel pump is brand new its a walbro 255 lph...i dont think the FPR is boost referenced...is there one i can buy would this solve my problem as far as going lean in boost??? idle is fine of course...

 

Paxton supply one
http://www.paxtonauto.com/product.php?id=135
Others out there
http://www.turbosmart.com.au/technic...s-an-fpr-work/
http://www.capa.com.au/fuel_regulators.htm

You would need advice on what ratio you require for you setup

Others are running without a FMU but using much way bigger injectors than the stock ones you have
http://forums.corvetteforum.com/c4-f...tors-size.html

 

Thanks for the info...if i buy an FMU i would have to make the lines up myself? im guessing thats not to hard right?...Now can i buy bigger injectors and not have a tune will the car run ok?..Im lost on this i thought these old school kits were bolt up and go...didnt think they needed all the add ons....

 

Welcome to the world of boost.

 

Yes thanks...lol...this is my wifes car..I have cough cough a fox body with a turbo..little easier to run boost then the L98 tpi car...LOL....

 

Hello,

I think this app for iPhone or Android can be of great help. It includes a section where you can determine your required injector flow, pump flow and even calculate the increase in flow by an injector by increasing the system pressure via the regulator.

I see it being used all the time by the guy that tuned my truck. May work for you too!

Hope this helps!

 

Thanks for the info...i have the regulator adjusted im thinking all the way its like 55 psi with the line connected...i dont think i can get it any higher...thats why i was thinking an FMU to really pump it up in boost...i dont know if it will work or not...but was wondering how they did it back in the day...they didnt have tunes...i just thought it was with adjustable reglators and FMUs...i could be wrong tho...

 

If you read the articles I linked it explains why you may have 55 psi at the rail but won't be getting that at the injector ,under boost

 

I did read the articles it kinda confused me...lol...I don't understand completely...

 

You have say 40 psi on the rail , when you have 10 psi boost it pushes back on the injector so you only have 30 psi available ,less fuel sprays.
Engine goes lean under boost

That is why you need the FMU to compensate for the boost; as the boost goes higher it increases the fuel pressure accordingly to compensate.

 

Ok makes perfect sense now...I got ya...Now to find an FMU I can use on the car...I know I can buy an FMU its just the lines I need to get or make...which im sure isn't easy....

 

Find a suitable location up front to mount the FMU

If running the stock TPI rails , you are have to disconnect the return line from the rail and assuming the FMU has -6AN fittings ,
use -6 braided line to connect the rail and the return line to the FMU.

Will require this fitting for the rail
http://www.summitracing.com/int/part...5erl/overview/

and this fitting for the return line
http://www.summitracing.com/int/part...jerl/overview/

to connect the AN lines

2 of these to connect to the FMU ,
http://www.summitracing.com/int/part...6erl/overview/
(different angles available )

 

Oh wow thanks for the info..now for the line do I order that by the ft? and if so I just have to makes sure its 6an the car is 6an?? right...thanks for all this help I really appreciate it!!!!

 

Most auto / speed shops have bulk hose ,you just buy what you need
The line you are dealing with is 3/8" which uses a - 6 AN fitting.

The stock fitting is metric ( 16mm ) which is why you need the adapter fittings I listed to convert to the AN line

 

Ok got ya...I looked at catech FMUs well the B.E.G.I fmus now there fully adjustable from 1.1 to 12.1 they said you can get it tuned really nice with that..OR should I buy a vortech one that is 8.1 put the adjustable regulator back to 42-44 psi and just use the set FMU it might be a little rich but it should be safe???...Also can I say use an 8.1 fmu if its rich can I adjust the FPR lower and let the FMU make the difference up...? thanks for all you help...