what size injectors

[dmj]

I am about to pick up a MHI 18g turbo for a really good price and was wondering what would be the best size injectors to run, can I use the EVO 8 injectors? I am not going to drag race the car I want it to run on pump gas only but need a little more power than the evo 3 turbo. The car will have an evo 8 mas So far car has 2.5 in exhaust, 2g ported o2 housing. 255 walbro,sx fpr ,new clutch,just rebuilt engine ,trans and transfer case.the car still has stock turbo,injectors and mas.All constructive comments and input are welcome.

 

660cc or 720cc denso's would be my choice.

 

what are you going to be using to control the injectors?

 

[1990ggsxnj]

How much boost will you be running. Even with an 18g, if you're only running 16 lbs of boost, you will be fine (yes, IMO) with the Evo 8's. Keep in mind you have less potential to go higher in the future though. A little more info on the engine would help. Was it a stock rebuild, or did you bore out and/or stroke? This too would call for better injectors, be it now or later depending on when you did the modification. Just my two cents. I usually go with better so I don't have to switch parts more than once.

 

[dmj]

This is a stock rebuild .I am looking for about 20 psi max .Once I get everything together I will be sending my ecm to Keydiver.

 

20 psi at good airflow will eat a lot of fuel. I would just go 720's and the keydiver chip and call it done. That way when you get bit by the bug to turn it up, you will be ok. plus, 720's aren't big enough to do anything to idle.

 

[1990ggsxnj]

^^ I concur with this. 20 PSI is pushing it. I'll be going with 720-880's myself, with Keydiver chip or DSMLink.

 

[belize1334]

I have Evo8 560s. My chip is burned for 595cc and I'm at about 87% IDC at 20psi on my s16g. Taking that as a baseline, I think your 18g will definitely go past what 600cc/min or even 660cc/min can support. I'd go with the consensus and get a set of 720cc/min. Denso makes an affordable set as does FIC and a few others.

 

OK, I guess I'm going against the concensus, but if you have a Walbro 255 pump and the SX AFPR, and IF you're sure that all you want to run is 20 psi, then I say you should just jack up the base fuel pressure to ~43, maybe even 47psi, and the EVO injectors will be fine. They typically flow 585cc or more. /ubbthreads/images/graemlins/dunno.gif

 

[belize1334]

^^ That's a good point. If you don't want to invest in new injectors, and if your fuel pump will support the flow at higher pressure, then you can increase the base fuel pressure and just have a chip burned for the effective injector size.

 

[iLLeffeKt vr-4]

If you already have the EVO injectors just run them and see how they are. Log IDC (injector duty cycle).
If they get close to 100% then you need bigger injectors or bump up the fuel pressure. If you didn't buy the EVO injectors yet go with some 660's or 720's as suggested above and get a chip to match. If you plan on going with DSMLink or other kind of a standalone then go as big as you can.

I remember my friend with a 1g running a fuel pressure of 50psi on his denso 660's and 25psi of boost on a 57 trim. Put down 434awhp.

 

Dude 550's and a safc . We put down 340hp with 450's with a good tune, you can stretch your injectors along way, when you start gettin up into the 660-720 range your goin to have to start pulling fuel out, and thats just a waste. Everybody wants to run 720's , that is way over kill for a street car. Buy a wide band, safc and run your evo's and HAVE SOMEBODY THAT KNOWS WHAT THEY ARE DOING TUNE YOUR CAR.
My 2 cents
Gage

 

I guess I was figuring at stock FP. What Keydiver said makes sense. Flowing 585cc at 47psi would be good for 20psi from an 18g.

Im smart enough to know that keydiver knows tons more than me. I am just a fan of a little extra overkill in the case you change your plans later.

 

Quoting gagegregory:
Dude 550's and a safc . We put down 340hp with 450's with a good tune, you can stretch your injectors along way, when you start gettin up into the 660-720 range your goin to have to start pulling fuel out, and thats just a waste. Everybody wants to run 720's , that is way over kill for a street car. Buy a wide band, safc and run your evo's and HAVE SOMEBODY THAT KNOWS WHAT THEY ARE DOING TUNE YOUR CAR.
My 2 cents
Gage



Running your fuel injectors static and tuning with an safc is a great way to get the job done!

 

[dmj]

thanks for the input guys I am going to stick with the Evo injectors,the turbo I have not purchased as of yet,I might get the Evo3 16g turbo that Forced performance has on sale for a little more than I was going to pay for the 18g this way I get a brand new turbo.I will have to give on some horsepower though.

 

[Lonewolf64]

How much horsepower do you want? Over 300whp is not hard to achieve with an evo 3 16g.

 

[dmj]

I really wanted about 340- 360 whp on pump gas.That would make me happy.like I said in my original post I am not going drag racing I want a healthy street car for the occasional "situations" that may present themselves.

 

Well, earlier you said "20psi max", and that is what I based my recommendation on. If you are serious about 350HP, then 20psi and 560's probably aren't going to do it.

 

[Lonewolf64]

I made 326whp this weekend at the dyno. Mods were Evo3 16g and full boltons. Pump gas, ~23psi. I was getting a little boost creep and got a few counts of knock up top, which pulled timing, so I had more in the engine if I had stopped the creep.

This is on a keydiver chip with no further fuel corrections, so if you take into consideration that fact, and the fact that some timing was pulled up top, I could have made 340-350whp that night.

 

[dmj]

Dilemma solved, after some friendly advice and careful consideration I have decided to lower my horsepower expectations to 300-325 range Ported Evo3 turbo,evo 8 injectors and mas.264 intake and exhaust cams optional.