Ive had 5psi on a hahn 16g setup for the last year and i decided to go to 10psi.......i have a completely stock rebuild and i put the 10psi actuator on and heres the thing.....if you push the gas all the way down, it hesitates, like you have to find a median in the pedal to get it to boost properly....and its not reaching the full boost i think i can get out of it.....also the other day, the fuel pressure regulator blew out or something and it started leaking there so i replaced it with another one......do i need bigger injectors? is the gas not spraying enough while im trying to get more boost? Not really sure what to do now.....its a 97 gs

setup/mods?

What is your fuel setup? I really hope you are not boosting 10psi on a bone stock system.

Additionally what are you using to tune? Wideband? EGTs? Your guess is as good as ours if you do not have any data logged to show what is going on.

When I ran the Hahn 16G basic turbo kit, I found that if the adjustment valve on the rising rate regulator was not turned in enough, the car would not reach 10psi of boost, and boost would not come on smoothly. If this is what you are experiencing, you need to adjust the valve immediately as you are running dangerously lean at WOT.

Just to clarify, you are running Hahns normal fuel setup which consists of 270cc/26lb injectors, BEGI rising rate regulator, return line, and Walbro 255lph fuel pump correct?

If so, I would be willing to bet this is an FPR adjustment issue.

yea everything is stock......im sure its the fpr thats giving me issues but how to i fix that? do i get an aftermarket one and put it under the hood? i also have stock injectors, the fmu setup, fcd from mike. have not tuned the car at all

You are overtaxing your fuel system if you are attempting 10 psi on stock injectors with your setup.

If you continue, be prepared for a new motor.

If you have an FMU, you are good in that department, but you may want to get a different rate spring if you are going from 5psi to 10psi. More importantly, do yourself a favor and invest in some bigger injectors and a new fuel pump.

You can safely run 10psi on 270cc injectors, just like myself and many others have done, and tuning the idle will not be difficult. But, if you have future plans of making more boost, you may want to get bigger ones. As far as the fuel pump goes, might as well get the tried and trued Walbro 255.

ok so bigger injectors will fix my whole problem? how big can i go? i have a set laying around but i have no idea how big they are....any way to tell? i have the 255 walbro in there already......do i need a different fpr? Also, what valve were you talking about adjusting ebster?

How big you want to go with the injectors is totally up to you and your personal power goals. If 10psi is all you want to push out of the 16G, 270cc's would be enough.

You mentioned in your above post that you are running "the FMU setup" which I assume means you are running a return line and an adjustable FMU. If my assumption is correct, than all you will need to do is change the internal FMU spring to a higher ratio when you increase the boost from 5 to 10psi. If I am not correct, please elaborate on the exact fuel setup you are running.

The valve I was talking about is the asjustment valve on the BEGI rising rate fuel pressure regulator that Hahn uses in their turbo kit. Since it sounds like you are NOT using a rising rate regulator, you can ignore my previous comment

i just have a regular setup......i have a 255 walbro, stock fpr, vortech fmu, stock injectors......how do you change the spring in the fmu? sorry for all the questions but im a little lost right now and what needs to be done.....i have a set of bigger injectors that are going in tomorrow, anything else i need would help. Also, i need to know where i can find the exhaust gasket for the hahn that bolts the turbo to the manifold......ive bought 2 steel gaskets and they leaked and then i made an aluminum one and it blew.....its the square one with for holes in the corners. thanx again

No worries for all the questions, but I really do recommend doing more research before you make posts like this. There is tons of information on this website as well as others about how to turbo our motor and what is needed in terms of fuel needs.

That being said, changing the FMU spring is as easy as taking it apart and putting a new spring inside. I never ran this setup, so I am the wrong guy to talk to about spring rates and what spring is best for your goals, but I know a lot of guys on here do run the Vortech FMU at different boost levels. Your best bet is to do some research on this topic as Im sure this has been discussed before. Just use the search option.

I myself have also had to change the turbo flange gasket in the past. Personally, I just went out to Hahn and ordered two of them. I found that with our application two worked better than one. You may also want to have your flanges checked for trueness. It is possible that yours may be warped.

they sell the recalibration kits for the vortech fmu......is this what i need and what ratio do i need to adjust to? i did do a search and nothing i found helped my situation....

If you get larger injectors, you need something to compensate the pulsewidths or it will run pig rich. Stock injectors can't push much more that 8psi, or your fuel line pressure will get outrageously high for a stock equipment setup, not to mention the injectors and fuel pump (even the Walbro) aren't designed to function that well at that high pressure / flow rate. You are undoubtedly running super lean, surprised you haven't blown it already. If you want to keep the stock injection setup, go with the PortFueler setup. Otherwise to get higher boost you need a different computer/injectors (even a SAFC might work, heard some people have luck with it).

For the gaskets, you may just need to plane the surfaces, they may be somewhat warped.

Lets not confuse him. He can safely increase the injector size and run a Walbro pump without the need for a secondary fuel control system. I ran 270cc injectors and the Walbro 255 for years on the stock ECU by using nothing more than a rising rate regulator. If he wants to increase injector size conservatively, he can run them on the FMU he has. I would just recommend reducing the idle fuel pressure and getting a new spring rate to compensate for the higher boost levels.

Now, if he wanted to increase the injectors substantially, lets say to like a 400-440cc size, then his idle would be pig rich regardless of how low he sets the idle fuel pressure. That is when something like the SAFC can be used to help lean the idle out.

And you had no issues with a 25% increase in injector size as far as fuel trim compensation? I don't see why that would even work, as lowering the fuel pressure just effectively makes a smaller injector. He will still have really high fuel pressures, and without anything to register boost for ignition or extra fueling (besides FMU) he's running a serious risk of engine damage. If he's wanting to go 'high boost', he needs to appropriately modify the rest of his system to match, that's all I'm trying to convey.

Yes, I ran the 270cc injectors, Begi rising rate regulator, and Walbro 255 at an idle fuel pressure of 42psi, and it idled at a perfect AFR of 14.7 all day long for years on the stock ECU. Never had an issue.

I ran this setup at 10psi of boost on stock internals with no ignition retard for about 5 years and 25K miles without issue. It was only when I increased the boost up to 13psi (wasnt done intentionally) that I had engine damage occur to a ringland.

If he is only looking to run mild boost, say 8-10psi, I dont see why he needs to compensate with anything more than an FMU, new injectors, and a new pump. Granted, at 10psi he will see high fuel pressures.

Originally posted by justins71
If you get larger injectors, you need something to compensate the pulsewidths or it will run pig rich.

As long as you lower the idle fuel pressure the ECU is fully capable of adjusting the pulsewidth to get correct AFRs. This is true for 440s at least.

270's I can bite, dropping to ~35-40psi would work, but 440's you'd need ~15psi fuel pressure to get about the same flowrate. Pretty crappy spray patterns at that pressure, and might work but not well. It can be bumped up, but the computer's trim window isn't that large IIRC and won't be able to compensate beyond a point. Plus with larger injectors the trim will be be skewed under load, as if you run something like a 6:1 fmu it'll be leaned in N/A regions but the trim will probably to positive at WOT when the FMU kicks in, unless you're exactly at WOT, where it'll be super rich again. Running a 12:1 gives the best linear results, but then the entire N/A region is trimmed lean, making it almost pointless running larger injectors unless there's a duty cycle issue (but with FMU's there shouldn't be as that's what they're there for to compsate)

I'm not tryin to get into a pissing match if you guys have run it and had success, it's interesting to hear what can/can't work when going beyond stock. Small mods are one thing, but he's still running stock pretty much everything and just wants to keep pushing more boost. He's going to blow something up if he gets it in his head that one or two little things can fix everything instead of approaching the situation understanding exactly how it things need to work.

Who said anything about him wanting to "keep pushing more boost" This post started because he wanted to increase boost from 5 to 10psi safely and wanted to know what fuel mods were necessary.

As I said above, he can safely and effectively run 10psi on the stock ECU with injectors as small as 270cc's and an FMU with the correct spring rate. The car will idle fine, and should have no major rich/lean issues at WOT or cruising.

I do agree though, that if he DID want to keep increasing the boost level, it would be wise to have a more advanced fuel delivery setup. But hey, I wouldnt recommend pushing more than 10psi on stock internals anyway. So at that point he would need to start thinking rebuild regardless.