Which injectors? (another post)

[laza101]

I have a 16g ported w/Supra side-mount and 190lph pump, stock injectors, intake and 2.5" exhaust. I am running 17+ psi on the street on 94 octane. My injector duty cycle is easily pegged at 100% and I think my timing is being pulled because of it (around 14 degrees at redline), my a/f is about .8-.85. (1990 tsi) I have a translator on the way...

My question is: Will 510cc injectors cut it if I want to run 19psi on the street and less than 95% duty cycle? Anybody have experience with injectors at ~300hp? ONLY INJECTOR COMMENTS/EXPERIENCES PLEASE. I don't want comments like "you shouldn't be running that much boost" or "raise the fuel pressure." I need to decide between 510cc and 550cc (I already have a set of 510's). Thanks for your help!

 

[THEDUKE]

Originally posted by laza101
I have a 16g ported w/Supra side-mount and 190lph pump, stock injectors, intake and 2.5" exhaust. I am running 17+ psi on the street on 94 octane. My injector duty cycle is easily pegged at 100% and I think my timing is being pulled because of it (around 14 degrees at redline), my a/f is about .8-.85. (1990 tsi) I have a translator on the way...

My question is: Will 510cc injectors cut it if I want to run 19psi on the street and less than 95% duty cycle? Anybody have experience with injectors at ~300hp? ONLY INJECTOR COMMENTS/EXPERIENCES PLEASE. I don't want comments like "you shouldn't be running that much boost" or "raise the fuel pressure." I need to decide between 510cc and 550cc (I already have a set of 510's). Thanks for your help!

I ran 450 on about this setup but with race gas.Sorry but turning the fuel pressure up would help. You will have to just try your 510 & yes turn the fuel pressure up & if it dont work you will need bigger.No one can realy say this for you because eage car is differant. Although you didnt say race gas if you were to run it you would be able to lean it down & get some timing.If you are getting knock when this timing is down you will probly have to add fuel ,what ever it takes. Hope this helps.

 

[Cirus_93TSI]

if ur at 100% with ur stock 450s i dont think 510s are going to be big enough to lower ur cycle duty and raise ur boost, if u keep it at 17 ur cycle duty should go down to around 90-95%, upping the boost to 19 will most likely put u right back to around 100%, and if ur timing is being retarded by the ecu turning the boost up will only create more knock and ur ecu will retard the timing more, making ur car slower
so the choice is really urs, the 510s will be ok for 17 psi, if u want more boost get the 550s or u will be in the same position u are now with the 510s, but if ur going to go out and buy bigger injectors i would get some 660s instead of wasting money on 550s, lower injector cycle duty is better and then u know u can turn the boost up more if u needed to and not run out of injector, ur going to need an safc or some other type of fuel control to use any upgraded injectors anyway, so u might as well get the 660s and lower the cycle duty back down alot

 

[laza101]

Thanks for the replies, guys. I have decided to try the 510's since I already have them and turn up the fuel pressure a little bit. (I'll try a NON-TURBO FPR, I've heard many different opinions so I'll have to try it myself). If all goes well I should be able to lower my duty cycle under 90%. I'll post the results in about a week...

 

[marksae]

Do you have an AFC or something to control fuel? Turning up the fuel pressure will help some, but you really need to have some sort of fuel control to compensate for the change in fuel pressure. Your ECU's fuel maps are based on factory base fuel pressures. Increasing the fp will not alter these maps. The AFC will.

 

[laza101]

I HAVE A TRANSLATOR ON THE WAY. With 510's and more pressure, I should be able to reduce fuel by 15% or more.

 

[THEDUKE]

Originally posted by laza101
I HAVE A TRANSLATOR ON THE WAY. With 510's and more pressure, I should be able to reduce fuel by 15% or more.

Also the more you turn your boost up the more the fuel presure will rise.

 

[out there]

according to a couple of guys in town here, it's a lot easier to tune with bigger injectors... one guy has a 50trim, and he uses 660s. someone else has a 60-1 and i think he's using 720s. if you use bigger injectors, you'll be able to run the big16 to the top of it's potential

 

[laza101]

I've finally tuned my car well (a little fine-tuning left) - I had lots of timing issues due to my 2g maf, but that's fixed now. Anyway, I settled on 550cc injectors AND 54psi base fuel pressure (Walbro fuel pump). Believe it or not my injectors reach 100% DC at 20psi boost!!! I can't believe I'm using so much fuel, my stock 450's must have been way over 100% DC. This is on pump gas, of course. The car is much faster since the injector install tho. I agree with Cirus, take a look at my mods, I could use 660's (right now my injectors are like 616's with the added fuel pressure). Maybe next year....

 

[out there]

HA, i'm running 680s with my 14b
can you say "overkill"?

 

[L2RTSiAWD]

I would say just get some 550's and save yourself some hassle.

 

[TwoLiterV8Eater]

Originally posted by L2RTSiAWD
I would say just get some 550's and save yourself some hassle.

He did

Although with the base pressure set that high, you are seeing over 70psi of fuel pressure at 20 psi of boost, that is probably negatively affecting the spray pattern of your injectors if I had to guess. Does anyone else see this as a potential problem?

 

[aliengotpsi]

I had 660's on now I use 550's with a 50 trim and ran 11.2 with 110 octane.

you can buy injectors here.Straightlinespecialties.Com

Kevin

PS dont buy used injectors. you will thank me later..

 

[TwoLiterV8Eater]

Kevin what kind of trap speeds were you seeing with the 550s and 110 octane gas? Also what kind of base fuel pressure are you using and what did your duty cycles look like?

 

[aliengotpsi]

Originally posted by TwoLiterV8Eater
Kevin what kind of trap speeds were you seeing with the 550s and 110 octane gas? Also what kind of base fuel pressure are you using and what did your duty cycles look like?

Hey,
I traped anywhere from 122- 125.7mph with the fuel presssure set at stock. I have no clue what my duty cycles where at.. I didnt think it mattered to me at the time.

Kevin Smith

Straightlinespecialties.com

 

[Scrymerr]

Injectors run most efficiantly between 60 and 70 percent duty cycle. Personally, I would go larger rather than smaller, get an FPR and such, and just tune down. This way, you ever wanna run more boost, or larger turbo, you just tune it for more air, rather than go buy larger injectors. Right now I am working on getting a MAFT issue resolved. Once that is done, a set of Denso 720s are going on with only a 14b.

Later,

--Dan

 

[Jaraxle]

The post started with him stating that he was aiming for 300hp. I disagree that "larger is better" if the stock ecu is being used with a piggy-back such as an afc. Looking at the EVO which used 510cc and then 560cc and then 550cc through the years. Anyhow my point is that for 300hp or so, mitsubishi used between 510cc and 560cc with the 4g63, so shouldn't we ? (when aiming for the same HP figures) My reasoning about the AFC with BIG injectors is this: the computer is "thinking" that much less air is entering, and will make timing calculations that are wrong (and maybe dangerous) based on that wrong information.. Not to mention injector dead-time and whatnot. Just my 2cents.

-J

 

[marksae]

660s should be the largest anyone should go when using an AFC. 660s require the same dead time as the stock 450s, so you shouldn't have any driveability problems with them. However, having such larger injectors may put you onto the more aggressive timing curve. Folks with 1g CAS's can dial back their base timing to compensate for this. Low base timing settings kills your off-boost power big time.