Fuel pump

Someone just PMed me this question. It comes up pretty often so I thought I would post it here for other people that may be making a similar decision in a similar situation...

Hey kevin, I had a question on fuel pumps. Basically
I want to build a mid to low 12 sec street car on pump gas and run 11's
on race gas. I am looking at the Walbro 255 which I have (not installed
yet) or the Walbro 190. I know that the 190 is capable of running 11's.
I also know that the 255 would need an AFR too. I heard/read that with
the 255 you could run 18psi on the stock turbo, could you also do this
with the 190? What injectors would I run with the 190 or 255 pump? Is
there any benefit to having the 255 if the 190 is adequate? I only want
to upgrade once, hence all the questions. Sorry for all the questions,
I guess I think to much into things, any info would be appreciated.
Thanks in advance.

PS On yeah, don't know what turbo I am going with. Its either going to
be the Evo 16g, an 18g, or the 20g. Havent really researched these yet.
I was leaning more towards the Evo 16g since it is a fast spooling
street turbo, but don't know if I can obtain my goal with it. Any info here
would be helpful too.


For your turbo options and ET goals, the 190 will be enough. A friend
of mine is now running my old TDO6H 20g (read: big) and trapped 124 mph,
with the 190 pump ;) The secret is race gas. You dont need nearly as
much fuel when you go to the race gas because you lean out ~15% or more.
This same thing applies to injectors too. Pump gas power however will
require more fuel. If your setup is good enough to support 18 psi on pump, either pump will be adequate.

The other argument, which you have made as well, is to just upgrade
once and be done with it. In this case go with the 255. But you will
absolutely need the AFPR. So it may come down to cost vs. need. If you can
spring 200-300 bucks for an AFPR, just use the 255 you already have, and
you wont have to think about pumps again unless you go for 10s :D If
you cant/wont spend that extra cash on the AFPR, sell the 255 and go
190, it will still support your goals. And as always, dont just take my
word for it, datalog to be sure everything is safe.
-------------------------------------------

I forgot the last half of the question in my original reply though. The EVO16g is a great new option, and will support your goals of 12s on pump and 11s on race gas. 11s on a 16g wont come automatically though, it will require a good setup, very good tuning, and near perfect driving. I ran a 12.0 at 115 in my buddys car though on a small 16g, the first time I drove it. So its certainly possible on the evo 16g. Mod list under Joe G's car on www.posracing.net. I would avoid the 18g if possible. And the 20g is a great turbo. But you'll want to go with an external gate on that, which is a good idea anyway. (I never liked internal gates, even on the 16g sized turbos.) It will easily support all of your stated goals. I damn near ran 11s on my TDO6H 20g from SBR, 12.0/117 (seperate runs ;) ). There is more to consider when choosing a turbo, but this is the bulk of it. Hope it helps.

not to hijack the thread but what kind of tires do you use?
have great 60fts but not breaking 120
are you on drag radials?

what's wrong with the 18g turbo? my mechanic swears by it, saying the the evo16g is not big enough, and the 20g is just too much lag for a FWD car trying to get off the line... and the only fuel tuning i'm running is a walbro 255, no afpr. is this bad? i'm at a crossraod right now with how far i want to push my spyder. if i upgrade the turbo, i'll surely have to do the fuel, and if i'm going to go that far with it, i'll surely do the suspension too. but also, i'm thinking of buying a GSX and swapping all my parts before i drop tons of cash into my spyder. and on top of that, if a certain deal i got going falls into place, i'll be buying a new M3 and put this project to rest for a bit...

Lag is overrated

95 GSXracer.. could u awnser the injector size for me with a walbro 190. My car is running pretty good right now but i would like to get alittle more out of it. Not for sure what size i should get.

not to hijack the thread but what kind of tires do you use?
have great 60fts but not breaking 120
are you on drag radials?

I run Dunlop SP Sport 4000s. All season tires. Size is 215/50/r17. I'm not sure if its the tires, or the hundreds upon hundreds of launches I have in that car. But I like them ;) No drag radials for me. Someday perhaps.

what's wrong with the 18g turbo? my mechanic swears by it, saying the the evo16g is not big enough, and the 20g is just too much lag for a FWD car trying to get off the line... and the only fuel tuning i'm running is a walbro 255, no afpr. is this bad?

The 18g just doesnt run as fast as the 16Gs do. Especially with the EVO16g, which flows the same as an 18g coincidently. With a FWD, people typically welcome the extra lag of a large turbo. Less likely to break the tires loose in the middle gears (1st is obviously hopeless regardless). I didnt mind the lag at all with my TDO6H 20g I always refer to, and I pulled 1.5s on that as well so it got off the line just fine (at 3300 pounds). I dont think you will suffer any loss over a 16g on a fwd. Not sure what your mechanic is getting at.

Running a 255 with no reg will cause your mixture to be tooo rich at idle and cruise. When boost hits however, there is no longer an issue. The problem is this. At low fuel consumption, like idle/cruise, almost all of teh fuel pumped up to the rail has to be bypassed back to the tank via the regulator to keep pressure where it should be. With the volume of fuel the 255 moves, the stock reg just cant bypass enough fuel. (just like when a wastegate cant bypass enough exhaust and you get boost creep. Consider this "fuel pressure creep" ;) ) You need a larger reg. At full boost you are consuming a large portion of that fuel that is pumped up to the rail, so the reg doesnt need to bypass as much fuel to the tank, and the reg is now adequate. Hope that makes sense. :)

95 GSXracer.. could u awnser the injector size for me with a walbro 190. My car is running pretty good right now but i would like to get alittle more out of it. Not for sure what size i should get.

Not sure exactly what the question is, so I'll assume you are running stock injectors with the 190 pump right now. Rather than base your injector decision on your pump size, base it on your power goals, or your turbo size. You will also need to take into consideration what fuel tuning device you are going to use (AFC, DSMlink, etc) and what fuel you want to focus your efforts on (pump gas monster, or race gas hero) ;) I can explain why, once you answer those questions for me. Turbo, goals, tuning device, and fuel. Rather than tell people what injector to get flat out, I prefer to give you everything you need to make the decision yourself, since you know your situation better than I do ;)

Im looking for low 11's. i have a Big 16G. Im using 93 octane gas. plan on using the S-AFC.

Im looking for low 11's. i have a Big 16G. Im using 93 octane gas. plan on using the S-AFC.

So you plan ro also run race gas for the low 11s, and run a bigger turbo in the future? Still tough to make a recomendation with this info. So will you never use race gas, or are you just saying that you will be running 93 most of the time (i.e. daily driver that goes to the track every now and then). Do you plan to upgrade the turbo to something large enough for low 11s? etc.

HEre are the basic guidelines. The AFC only has +- 50% range. Running 660s pushes the limit if you plan to use race gas. You need -32% just to compensate for them, leaving only 18% to lean out with race gas ;) For this reason people have gone from 550s to 660s and gone slower... After giving up on it, they go back to 550s and go faster again. keep this in mind.

A new solution to this problem, which is especially useful on 1gs with thier shyte airflow sensor, is the MAFT GM maf conversion. You can use the MAFt to compensate for the injectors, then do all of your tuning with the AFC, again having the full 50% in both directions. Since the 1g sensor is shyte anyway, its a good upgrade at only ~300 bucks with sensor. Good for 1gs and 2gs in the sense that you can run it in blow through to run your big BOVs vented to atmosphere with no side effects, VPC style.

If you never plan to run race gas, you can use 660s no problem with just the AFC. Even 720s. But 850s are pushing it (-47% just to compensate for size) and shouldnt be used. If you are going to run DSMlink, I think you are good to about 1200cc injectors. 550s will do mid 11s on race gas, but you'll want at least 720-850s to do this comfortably on pump gas. Big difference ;)

Now, for a 16g and race gas 550s will be all you need. If you plan to try to max out the 16g on pump gas you may need 660s, making running race gas tough if you ever decide to try it. You really do need to run race gas to max out a turbo, and the 16g will get into the high 11s with very good setup, tuning and driving. 44-45 lbs/min (EVO 16g maxed out/20g at ~22-24 psi)will max out 660s on pump. Which means that by doing a straight ratio 550s will max out at 37 lbs/min which is doable on small 16Gs.

With DSMlink, go the largest you can do avoid ever having to upgrade again. I have run 550s, 660s, 820s, 850s, and now 950s. LMAO. With say the AFC and MAFt, you still shouldnt go too large because it will adversely affect the ignition timing advance.

This may raise more questions that it answers, but choosing injectors is a tricky subject unless you ensure you have enough range to cover your needs.

I will use race gas every once and a while. 550cc injectors are 18% bigger than the stock injectors. so i figured they would get me to where i want to be. Also the larger injectors should also help out with fuel cut correct? OH also i forgot to tell you i have also done a 1g head swap. If that helps this out any.

550s will allow you enough range to run race gas. They will also be enough for pump gas but you'll be on the line, so be sure to datalog and be sure its all safe if you start to turn up the boost on pump gas (over 20 psi, requires FMIC, etc, but it is done). 18% bigger injectors will allow you to flow 18% more air before you hit fuel cut. It may not be enough. A friend of mine is on a 1g with evo16g and with 660s is still hitting fuel cut. If you dont plan to get a TMO or similar chip to remove fuel cut, you may want to look into a MAFt and 660s. The EVO 16g will also outflow the 1g mas anyway when you start to crank up the boost on race gas.

Thanks for the help man!

No problem :) Hopefully I've steered you in the right direction and your project goes well.

alright, i think i get the jist of this but one more question... Evo 16g, FMIC, 660 or 720 injectors, now heres the question>> i will be running either a AFC or DSMlink, now can i use both? i have both just sitting here and if i can use both i will, if not i will sell the AFC then!

There is nothing you could do with the AFC that couldnt be done (better) in DSMlink. So by all means, get what you can for it. Most poeple that bought DSMlink didnt really pay for it. Sell the AFC, TMO chip, and OBDII logger, and its payed for :) If you are going dSMlink, you may want to consider even larger injectors, since there are NO drawbacks or negative affects in using large injectors with DSMlink. Basically none of the stuff in this thread even applies. DSMlink is the ultimate solution. I might suggest 850s unless you are sure you will never be looking for a larger turbo and 400-450 whp on pump. Its your call. Good luck.