How much boost should I run?

[odormat000]

I am about to have my car tuned and I would like to know how much boost I should run. My car is a daily driver but I'm not worried about boosting so much my turbo blows up. I'm looking to have over 300hp with this set-up and want to max my stock turbo.

A little about my car.
91 Plymouth Laser RS
upgrades:
3 inch intake
FMIC
GM MAF-T
crushed 1g bov
evo exhaust manifold
ported 14b
ported 2g o2 housing
3 inch turbo-back w/ test-pipe
walbro 255
boost controller
272 cams
3g lifters
arp studs


I have the stock injectors and I was wondering how many pounds of boost I can max my 14b to with them.

I am also looking for a 7cm manifold-turbo gasket. I went to baxters and they had one for $40 and I figured I could find something much cheaper.

Any other advice on things to do would be appreciated thank you

 

[Aceman]

Trying to figure it out this way is ridiculous. I think what you need to do is look at a compressor map, I can't find a good 14b one so here is an 18g as an example:

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You add 14.7 to your desired boost level, then divide by 14.7 to get the pressure ratio and then you have match up the airflow numbers. I think thats how you do this...its been a while since I had to think about this stuff.

There are alot of factors. If you wanna learn it all read this:
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

or...

If you don't wanna try to become a math major over night just set your psi low until you can log.

I think I've edited this post too many times, I just remembered this, scroll down to the injector chooser assitant:
http://www.roadraceengineering.com/eclfuel.htm

 

[snowborder714]

Ok but how do I relate that to what I have?

I think you need to take a look at Scott's post again.

The 255 will be able o supply the fuel to the rail but the injectors can only inject so much before they they are to the point of staying open to "meet" fuel needs; injector duty cycle.

It's just like a metal chain, it's only as strong as the weakest link. You could have a chain made of titanium and a link made of lead. Sure the rest of the chain is strong but it will break at the lead. Same principle as your fuel system. Strong pump, way to tune, and AFPR will still limit you to stock boost settings because the injectors are too small and cannot keep up regardless of what you do.

Here's a compressor map I found for a 14b. Hopefully it's right.

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On the compressor map above, 2.0 PR = 15psi. The associating .20kg/s air flow rate = 26.46lbs/min.

Yes, your pump can support 59.93lbs/min at 15psi, but your injectors can only support 25.84lbs/min at 80%, which is around the ideal max you'd want to run. If you compare what your injectors can support to how much you're flowing from the above line, you'll see you're already flowing more at 15psi than your injectors can support flowing 80%. If your turbo is pushing 32.30psi, then your injector IDC is at 100% (i.e. they are constantly open and not pulsing anymore as they should).

 

[FluidKaos]

The Wally 255 is the strong link in your fuel equation. It WILL supply the fuel for anything you throw at it (within reason) outside of race applications and really big stuff. Stop worrying about the fuel pump and whether it can flow the fuel. The injectors are the weak link. The max flow rates for the 450's have been given to you. The link I gave you has calculators that will let you work out all this info for various boost levels, and fuel pressures, and air flow rates. Just click on the 'Technical' link on the left, and bask in the mass of information (Including Compressor maps for a lot of turbos)