Walbro 255 + 450cc injectors + more PSI = ????

[gijoe985]

So, I know that with an increase in fuel pressure, you can effectively increase the amount your injectors can flow. A calculator I used gave that 450cc injectors at 43psi = 550cc(ish) at 65psi. I also know that as pressure increases, the pumps ability to flow decreases. So, even though the pump can produce up to 85psi before the internal relief valve kicks in, you would not be getting optimal flow.

My question, how high can a walbro be turned up and still flow the needed amount for that psi? I think I phrased that correctly. So, if I ran my 450s at 65psi, would I be able to get the performance of a 550 out of them?

I'll admit that this is more out of curiosity than what I plan to do. Though I love backyard DIY mechanic performance and just like learning more about what can be done. I bet I could find the walbro flow rates somewhere. Just got to look.

EDIT- found this chat- http://www.autoperformanceengineering.com/html/fpspecs.html but I guess that leaves me needing to kwo what my fuel needs would be at 65psi...

 

[Chicken Patty]

I found that Walbro 255HP's bleed off starting at 75PSI. So whatever your base fuel pressure is plus whatever your boost pressure is is your total PSI. Keep it under 75PSI. For example to get the most out of my buddies 1200cc injectors on the dyno we cranked up fuel pressure to 45psi base and then the car was at 30psi. That totals for about 75psi. We tried slightly more fuel pressure and car actually went leaner. Hope this helps.

 

[Mecheng1993]

It's not great for your injectors to run too much fuel pressure through them, so you should definitely upgrade them anyway. I am running Evo injectors (560cc's) on 45PSI of fuel pressure, but for some reason if just makes me weary.

 

[gophishy10]

If you have link, keep an eye on your idc's...that is if you actually intend to do this.

 

[Diamond Star Werks]

It's not great for your injectors to run too much fuel pressure through them, so you should definitely upgrade them anyway. I am running Evo injectors (560cc's) on 45PSI of fuel pressure, but for some reason if just makes me weary.

You realize your fuel pressure increases 1 to 1 with boost pressure right?

 

[DSM1G90]

VR-4's, stock, came with 510's and a B16G turbo, not 450's and 14B as with the other 4G63 Turbo motors found in the DSM line. Motor ran 225HP stock with this setup.

I found that out the hard way when I got my Laser with wondering why I was running so rich. Thing had a JDM VR4, 4G63 with the 510's and the B16G. Thus, I pulled the 510's and put in 450s to get my system back in balance .. all to match the stock ECU.

A 'Wally' 255 needs bigger injectors to really make things work along with a modded system.

 

[LandSpeed-DSM]

http://www.dsmtuners.com/forums/newbie-forum/422900-things-not-do-14b-450s-boost-turned-up.html

 

[Chicken Patty]

http://www.dsmtuners.com/forums/newbie-forum/422900-things-not-do-14b-450s-boost-turned-up.html

On a small 16G at 16psi I was running 82-84% IDC with simply a Walbro 255HP pump as my only fuel mod. Stock FPR and all.

If he has a way of logging the car, he can turn it up as long as IDC is okay. He can turn it up some, just not a lot.

 

[gijoe985]

VR-4's, stock, came with 510's and a B16G turbo, not 450's and 14B as with the other 4G63 Turbo motors found in the DSM line. Motor ran 225HP stock with this setup.

I found that out the hard way when I got my Laser with wondering why I was running so rich. Thing had a JDM VR4, 4G63 with the 510's and the B16G. Thus, I pulled the 510's and put in 450s to get my system back in balance .. all to match the stock ECU.

A 'Wally' 255 needs bigger injectors to really make things work along with a modded system.

I have never, ever, heard this... But maybe I just have never stumbled on it. I'm going to look this up. Is that only JDM galants?

 

[DSM1G90]

Is that only JDM galants?

All of the Galants - Galants VR4 were made in Japan for both markets and the Galant line is still manufactured over there.

Those 91-92 VR4 Galants were total screamers out of the factory due to the size of the chassis-being bigger than the DSM of that era. They had the same 6 bolt block specs as what's in the DSM, but ran a slightly larger intake to work with the 510 injectors and the B16G turbo and using premium fuels to get that 30 more HP stock. You might say Mitsu in Japan wanted more intake to get that power out of that motor.

They also had a big brother to the Galant and that was the 3000 GT with that dual turbo 6G72 V6 road stomper during this era. DODGE got into the Mitsu sports car by staying away from DSM and taking that 3000 GT and calling it the STEALTH.

DSM's were made in Normal, Illinois at the now-called MMMA (Mitsu Motor Manufacturing of America) plant. The 4G63 Turbo setup was downsized a bit for the smaller chassis

Are your injectors blue tops (450cc)? VR4's used yellow tops (510cc).

 

[kchaazz]

I thought that the 510cc yellow tops were pretty rare to find when getting a JDM motor, and that it was a small 16g that came on those? Ive seen half a dozen motors with the red valve cover, ordered from supposed JDM motor shipping companies, the motors in question presumably coming from a GVR4, and have never seen the 510cc yellow top injectors on them. Im just curious to know more about this, if you have any more info.

 

[DSM1G90]

Im just curious to know more about this, if you have any more info

I did a Google search on the Galant VR-4 and found the specs on the engine and drivetrain that this vehicle contained. It showed the injector size - being the 510 - and the size of the turbo used.

Give you a bit of history on what I found out(and in the hard way): 2008, is when I bought my Laser from a local dealership. Vehicle had 161K on the clock. Took the thing home and did a total belt kit on the motor along with NGK BPR6ES plugs gapped @ .028.(thing had Denso plugs that were way too hot and still looked cruddy..)

Got it on the road, had decent power, but the thing was stinking of a rich mixture. Checked the timing - CAS was cranked all the way advanced. Retimed it to specs and still that rich mixture in the exhaust (Oh, and did have a CEL due to a bad knock sensor-did the beep test on the ECU and got that replaced in a quick) during idle. Checked plugs and they were dark from burning a rich mixture with timing back into specs.

I then put two and two together and figured out when I saw the injectors .. being yellowtops instead of bluetop 450's that the ECU was designed to work with for this series of DSM's. On the valve cove, one can barely see, written in grease pencil, the markings of "VR-4 4G63". The valve cover, which isn't a red valve cover, contains NOT the "DOHC '2000" , but "Mitsubishi 16 Valve" making this cover was used on the Galant that used the 4G63.

Luckilly, in a yard close to me, a wrecked Turbo Eclipse came in with bluetops (head was already gone along with the turbo) intact in the intake manifold. I snagged them bluetops, bought the "O" ring and seat gasket kit for the injectors, took the yellowtops out and put the bluetops in and my rich condition was eliminated .. along with getting tonnage of more power from that B16G (I checked the serial number on the housing to get the results being a B16G) and have been a happy camper since .. and driven the car twice arond the western part of the country and have logged 29K miles since I bought it.

I still have them yellowtops.

This is the one trick that all modders need to pay attention to: START with the ECU, Then work backwards to the injector size, then to the fuel pump.