Why do I REALLY need larger injectors than 450s for a Big 16G?

[4gfun]

Just don't want to waste my money, and I am very curious about this since this is my second DSM.

Both of my DSM's were/are alleged 12 second cars. I noticed that both of the previous owners ran 450 cc injectors on them.

This all seems to be too much of a coincidence for me, it really does.


In addition, I have read that Bushur had run 120 mph trap speeds on his DSM but turned up the Fuel Pressure.


If I want to run 22 psi on the street on pump gas, is it REALLY a MUST that I upgrade my injectors?

Thank you for your time.

 

[4gfun]

Well for the obvious, IDC over 90% in any gear at WOT is not a good sign. Did you do that log with the crazy fuel pressure? I would adjust it back down to stock FP (37.5psi with line off) and do another log, just to see where IDC sits. As far as WI goes, I would definitely recommend getting a meth kit. I know i'll be getting one soon too. Either way, my personally suggestion would be to get the 550's or 660's first then get meth.

For reference, back when I was running a e316G + 660's, I was getting ~85% IDC @ 23 psi with a walbro 255 and no AFPR.

Yes that is when I ran it with the wacky fuel pressure e.g. 57 psi with the line off.

I'll try it again to be sure that IDC is way off.

Thanks!!

 

[steve]

Yes that is when I ran it with the wacky fuel pressure e.g. 57 psi with the line off.

You can't run the car with the Fuel Pressure Regulator reference line off unless you want to blow up your engine.

As you noticed the pressure changes when it's connected and that a good thing because as the manifold pressure changes from vacuum to boost the fuel pressure rises to keep a constant differential pressure across the injectors so they always flow the same amount of fuel. Without it the higher the boost pressure the less fuel that would flow until none flows when the boost and base pressure are equal. Not exactly what you want to happen at WOT.

 

[4gfun]

You can't run the car with the Fuel Pressure Regulator reference line off unless you want to blow up your engine.

As you noticed the pressure changes when it's connected and that a good thing because as the manifold pressure changes from vacuum to boost the fuel pressure rises to keep a constant differential pressure across the injectors so they always flow the same amount of fuel. Without it the higher the boost pressure the less fuel that would flow until none flows when the boost and base pressure are equal. Not exactly what you want to happen at WOT.

When I said "ran" I meant at idle.

 

[flinguist]

You can get injectors for cheap on EBAY. Just keep looking until you find them at the price you're willing to pay. I got 720's for around $150. I had them refurbed just to be safe, and still ended up spending less than 200 bux.

 

[Black_Bullet]

What me and all my dsm friends did when we first got our evo3s before having money to get injectors is run the n/t fpr which has a base fuel pressure of 47.6 psi and still rises 1:1 with boost.
You can find them on the non turbo 4g63 dsms in the junkyard for next to nothing.
This added fuel pressure will make your 450s flow about 505cc worth, so if you have eprom tuning you just have to tell the ecu your compensating for 505cc injectors or whatever the case be. I run FIC 850s now and i still use the higher fuel pressure to push me closer to 900ccs.

I wouldnt ever run more than 50psi fuel pressure, the only reason to do it in the first place is if your out of injector. Say if you have like e85 and you already are running 1600ccs and your trying to make like 700whp or something it may be neccessary. I dont know but higher fp It has its pros and cons i believe it can help with fuel pressure over run since your starting at a higher pressure to being with, and on most setups ive seen the over run spikes to around 48 psi which wouldnt be over run on a car starting at 48psi base. This is all theoretical in my mind about the over run i may be completely wrong though.

Anywho; with this n/t fuel pressure reg. and the car tuned at 11.5 afr w/ 19degs of timing
( Ive normally heard to shoot for 11.1 but i was trying to get more IDC's out of the 450s )
with stock motor and fmic and with other upgrades and supporting mods ( i.e. intake, exhaust, fuel pump )
I was able to wring out 17-18psi with no knock and a 90% idc. If I tried running more than 18 the afr would probably begin to lean out as the IDCs quickly rose at that point.

 

[MattratfTSI]

I suggest you start increasing the boost and watch knock and IDC, you'll see how fast your injectors hit 100%.[/QUOTE]

what is IDC?

 

[Colt4G63 also]

I suggest you start increasing the boost and watch knock and IDC, you'll see how fast your injectors hit 100%.

what is IDC?[/QUOTE]

"Ignition Detonation Count" or something to that effect. Enough of that will shatter pistons or bend rods.

It's what happens if your A/F mixture ignites before it's supposed to, due to heat from compression. Feel free to mark this post as helpful.

 

[dsm-onster]

^^^ Injector Duty Cycle.

It is the percent of time the injector is open of the overall time the ecu can allow it to be open.

 

[MattratfTSI]

is it possible to have too big of injectors? Im pretty much stock right now and im putting in 850s and an safc. is this ok? will i be able to tune the 850s down enough for like 18psi on pump gas. are these injectors just too big for my setup or is there really no such thing as too big if I have a fuel controller?

 

[Colt4G63 also]

Doh!

 

[kevbojunior]

You would def. need atleast a 190lph fuel pump and 510cc injectors. I dont know where you could get those injectors though but ive seen them.

 

[fatherbubble]

I first tried my Evo III 16G with stock injectors at 18lbs of boost you'll get 108% duity cycle. At 24lbs you'll get a rod knocking an a couple fried valves. the good thing your car will still run, but you'll have alot of noise from it.

 

[dsm-onster]

You can't get a knocking rod from running too lean with stock injectors!!!! ??? Rod knock and knock from detonation are entirely different.

You can run stock injectors with an evo3 16g. You can't run ANY turbo with stock injectors at 18+ psi and be remotely safe.

 

[PIMking]

take a look at this. This was my car on a 16g.

http://www.dsmtuners.com/forums/newbie-forum/303648-why-i-blew-my-motor-pics.html

just suck it up and get bigger injectors. you will go faster with them.

 

[kevbojunior]

I agree, just get bigger injectors. they wont hurt the car if ## running stock boost or anything. they will only flow what u tell the computer too let them flow. then if u wanna crank up the boost and fuel u have the supporting mods to do so.

 

[SOADweskey]

is it possible to have too big of injectors? Im pretty much stock right now and im putting in 850s and an safc. is this ok? will i be able to tune the 850s down enough for like 18psi on pump gas. are these injectors just too big for my setup or is there really no such thing as too big if I have a fuel controller?

Those injectors are to big to work properly with an AFC. I'm sure you will get the car to run but since the AFC only changes performance at wide open throttle you will always idle and cruise very rich. You either need a better tuning solution or injectors that are 660 or smaller.

 

[steve]

since the AFC only changes performance at wide open throttle you will always idle and cruise very rich.

The low throttle settings are usually the closed loop corrections. Your correct that the 850s are a little big for an SAFC, but not correct that the SAFC only changes performance at wide open throttle. You can't really change the AFR except during open loop but the SAFC corrections are always applied before the ECU even sees the airflow signal.

 

[SOADweskey]

Thank you for the correction. I don't have much AFC experience. I was tempted early on in tuning with all the extra feature of DSMlink.

 

[91AWD4G63]

ok so since we are on the whole 16g and injectors thing I got a question too. I have a 91 gsx automatic (came with 390's) but I can get the 450's for free from a friend can I just plug these in along with my big 16g and run around 16 psi?

 

[steve]

ok so since we are on the whole 16g and injectors thing I got a question too. I have a 91 gsx automatic (came with 390's) but I can get the 450's for free from a friend can I just plug these in along with my big 16g and run around 16 psi?

The automatic came with a different fuel pressure regulator than the manual that runs the injectors at roughly 43.5 psi rather than the 36.3 psi on the manual cars. That will give you a little more fuel capacity from the injectors (they will be 450cc rather than 411cc). The ECU automatic ECU is programmed for the 390cc injectors so you will have to correct with a SAFC, MAFT, DSMLink, or a EPROM chip for the change in injector size.

The rest of this thread applies to your basic question, can you run 16 psi on a 16g. The answer remains it depends on your tuning and the injector duty cycle at WOT with your tuning. It might work but you'll be better off with bigger injectors.

If you haven't read the whole thread I suggest you do.

 

[91AWD4G63]

Yeah i was reading and all i could find was people running like 18 psi or more I dont wanna get all crazy like that until i do get dsmlink just something to drive around and spank hondas

 

[JayRolla]

What me and all my dsm friends did when we first got our evo3s before having money to get injectors is run the n/t fpr which has a base fuel pressure of 47.6 psi and still rises 1:1 with boost.
You can find them on the non turbo 4g63 dsms in the junkyard for next to nothing.
This added fuel pressure will make your 450s flow about 505cc worth, so if you have eprom tuning you just have to tell the ecu your compensating for 505cc injectors or whatever the case be. I run FIC 850s now and i still use the higher fuel pressure to push me closer to 900ccs.

I wouldnt ever run more than 50psi fuel pressure, the only reason to do it in the first place is if your out of injector. Say if you have like e85 and you already are running 1600ccs and your trying to make like 700whp or something it may be neccessary. I dont know but higher fp It has its pros and cons i believe it can help with fuel pressure over run since your starting at a higher pressure to being with, and on most setups ive seen the over run spikes to around 48 psi which wouldnt be over run on a car starting at 48psi base. This is all theoretical in my mind about the over run i may be completely wrong though.

Anywho; with this n/t fuel pressure reg. and the car tuned at 11.5 afr w/ 19degs of timing
( Ive normally heard to shoot for 11.1 but i was trying to get more IDC's out of the 450s )
with stock motor and fmic and with other upgrades and supporting mods ( i.e. intake, exhaust, fuel pump )
I was able to wring out 17-18psi with no knock and a 90% idc. If I tried running more than 18 the afr would probably begin to lean out as the IDCs quickly rose at that point.

I used to run a n/t fuel pressure regulator too. I was getting 100% IDC's on my 550's at 22psi on my evo16g even with the n/t fpr. This would cause tons of knock to come in and I hated that I didnt go larger at the time. Only problem running the n/t FPR was it made tuning a pain with just the SAFC. I had to pull tons of fuel out of cruising because it ran crazy rich.

Now with the 1200's on e85 I see 69% IDC max. I have a little room to grow now.

 

[doober75]

octane, timing, and EXTRA FUEL it throws into the engine. meth injection has allowed me to get 23psi out of my 650cc injectors on a holset hx40. im sure he can run around 20 ish psi with stock injectors and a 16g with meth...

im about in the same boat as you. and agree 100%
of course with data logging

 

[4gfun]

Well all, I am back in the game. Lol, it isn't what you think either. Well I did wreck my engine, but it was because the timing belt flew off and bent all the valves!

I know this is an old thread...but I see that you have been replying to it for half the time since I left.

I have a 91 GVR4 now . The question is still on topic too. This time, I am not going to skimp out on injectors .

Based on that, do you guys have any idea what the optimal injector size is for a Big 16g if I plan on running high boost on 93/94 Octane and never plan on going with a larger turbo?

That's right, my GVR4 has a big 16g too.

I plan on pushing boost as high as some of you have on the 16g e.g. 22-23 psi on pump gas and I want to make sure that the 550s can handle it.

I won't be limited by the SAFC this time either. This GVR4 came with an EEPROM ECU and Ostrich Emulator.

Thank you for your thoughts! Everything in this post seems to indicate thta 550s will be enough, but some time has passed and I wasnt to see what you all think and if I understand correctly.

 

[Turbo Monk3y]

New EVO's, 16g type turbo, 560cc injectors = OEM reliability. Seems that they are on to something huh?