2G Injector choice

[madquickyo]

Hey everyone, im new to the forum, so first and formost id just like to tell everyone what up.

I have 650cc injectors and I was wondering if anyone here would be able to tell me if they are good enough for the setup I now have. They were for my last setup on my car, but I am rebuilding it again and doing more work to it. Here are my engine mods:
1g TB, 1g CAS, 650cc Injectors, Fidanza Adjustable Cam Gears, Moded Stock Fuel Rail, Aeromotive Rising Rate FPR, Apexi N1 Downpipe & Exhaust, ARP Head & Main Bolts, BS Elim. Kit, Clevite Bearings, DNP Tubular Exhaust Manifold, Eagle H-Beam Rods with ARP Bolts, EGR Block-Off Plate, FFWD Butchered Crank, FFWD Level 3.5 head w/ Fererra 1mm SSValves, Crower Springs, Titanium Retainer, FP2 Cams, FP 3' Intake Pipe w/ K&N Filter, FP Green, Greddy FMIC w/ Piping, JE Forged Pistons (20 over) Magnus SMIM w/ Nitrous Bungs (no nitrous yet though), Mitsu Metal Headgasket, MSD DIS2, MSD Fuel/Tach Adapter, MSD 8.5mm Wires, NGK Plugs, Ported O2 Housing w/ Tial 40mm Wastegate vented to atmosphere, SCE Gaskets, Tial BOV, Unorthadox Underdrive Pully Kit, Upgraded Steel Braided Fuel Line to -6AN, Walbro 255lph Fuel Pump re-wired w/ 10g wire.
Right now everything is tuned on my Super AFC and Greddy Profec B spec 2...but I have a DSM link on the way also thanks to FFWD. Also in the process of finding a good water injection kit.

See, I have recently gotten the head and crank from FFWD with other misc. parts from them and my SMIM and my FP2 cams from FP and other parts from them also. Everything was running good before I bought them. I took my car to FP last year and got it tuned and everything worked flawlessly together.

My question is with the recent work I have done, would they be big enough or would I need bigger than 650s?

My car was an automatic, but I did a 5-speed swap and will soon be ordering my clutch kit and flywheel. Does anyone have any specific kind to go with? I was thinking the ACT 2600 clutch kit with act XACT flywheel. Or would CM or Exedy be better?

 

[4geze63]

I think you should be ok, I see alot of people with 720s with that set-up, which isnt a great deal higher. only one way to find out

 

[PaleDSM]

I'd go with a larger injector. You have a similar setup to me (few more goodies) and I am going to be running out of injector with my 660s on high boost settings. With DSMLink large injectors will idle like normal so there really is no down side to going larger.

For a clutch I have used nothing other than ACT clutches for a long time. It is what I will buy again the next time around, whenever that may be.

 

[Kevin Jewer]

With DSMlink there is absolutely no good reason not to go right to large injectors, like FIC 950s. In fact DSMlink just released a new client that can provide compensation for the 1600cc injectors, but with that much of an increase, there may be some IPW resolution issues at idle, still waiting for some data. But 950s are a no brainer. I've upgraded injectors at least 5 times, all it does is waste mod money. My 950s idle fantastic with DSMlink. With AFCs and other airflow modification tuning devices, its not nearly so simple. Without at least injector compensation chip or other means to correct timing, you typically want the smallest you can safely get away with.


The size of the turbo is a very important factor when I determine what size injectors are required, and I'm either blind, stupid, or its not in your mod list there. I like to look at the turbos maximum flow, and size the fuel system for that. That way if anything goes wrong with boost control, or you get greedy, there is enough fuel supply. No matter what your mod list is you'll have a real hard time flowing more than a couple lbs/min over the turbos rated capacity.

The important pieces of info are max airflow capacity, target air-fuel ratio, and the Specific Gravity of the fuel. If there is some interest, I can put together a thread that explains exactly how to calculate this. Same principle applys to fuel pump sizing, but you also need to know the pumps flow rate at the pressure you intend to run it at.

 

[madquickyo]

Thanks for the help guys. Thats basically what I was thinking now that im getting my DSM link, go with bigger ones. But im not certain which size to go with. I do also want to get a bigger turbo in the future, but im still debating what one to go with also.
95GSXracer, right now I have an FP Green turbo. I dont know much about tuning either. Im going to start to learn how when my car is running again and ima post on the tuning foums a little bit. So yes, I am interested in that thread. It would help me out a great bit.

 

[dynatos]

if you wouldn't mind putting everything into a tech article/thread that would be wonderful

 

[Kevin Jewer]

I'll do that a bit later. Maybe tomorrow. But to do some quick numbers, a 50 trim is rated to about 50 lbs/min. 4 750s, with a target AFR of 11:1, and fuel specific gravity of .76 (average for pump gas), are good to 55 lbs/min. Just enough headroom. But I will say once more that I highly recomend just going right to 950s with DSMlink. They idle like stock, and under the same conditions given above they are good to 70 lbs/min. Bigger than the 56 trim/GT35r sized turbos by roughly 5 lbs. Change from pump to race gas (specific gravity of .724 for the 117 octane fuel I run) and from 11 to 12:1, and you get a little more capacity at 73 lbs/min. Of course this is all math, but it has been very accurate in my personal experience.

 

[dynatos]

you think that a maft would be able to adjust well enough for 950's?

 

[Kevin Jewer]

I dont remember what the range is on the MAFt, but it would have to be at least -53%, preferably 55-60. At any rate, even if it has the range, I wouldn't recomend it. Timing is going to be WAY off with that much of a drop in the airflow signal. If you NEED injectors that big, and thats what you are tuning with, you can make it happen (pull some back with the 1g CAS, etc). But its not a very clean solution. If you are using a MAFt/AFC/etc, I recomend using the smallest injector that still gives a little headroom. A chip with injector compensation is the next best thing, but if you have an EPROM ECU you might as well spring for DSMlink, IMO. But a chip with compensation will allow you to run big injectors without throwing timing off. And its relatively inexpensive if you already have an EPROM.

 

[sweet97]

I've got an AGP RS49 50 trim and tried 720's with my maft and had to lean it so much that I got way too much timing. 950's would send the timing through the roof!

 

[4sfead]

That is why it is very important to have injector compensation like stated above. The timing maps are WAY too aggresive with very large injectors. You have to have compensation. EPROM Chip or DSM Link.