So back when I did research for my fuel system I didn't anticipate as much room for "future growth" as I should have. I also didn't at that time fully understand BSFC numbers and just how much extra fuel E85 needs with a power adder. So long story short, right now I have Holley 76# injectors run at 60 PSI. The reason I need so much injector is because I'm running dry nitrous. So I don't have fuel jets or a fuel solenoid. All the extra fuel for the nitrous comes through the injectors. So with a direct port 100 shot, my current injectors are about maxed out with around 60% ethanol in the tank. My goal is to go up to a 200 shot on straight E85.

So I'm looking to get a new set of injectors. Something around 90 to 100# at 60 psi would give me a cushion as far as duty cycle goes. So the two I'm looking at are Holley Terminator 522-108X (100# at 60 psi) and the Siemens Deka IV FI114991 (93# at 60 psi).

Both sets are offered with a "matched set" option. I understand the benefit to a point. I just don't know if I would notice it in a street car. The price difference is as follows.

Holley Terminator 522-108X non-matched $378.95 matched (within 1%) $557.95

Siemens Deka IV FI114991 non-matched $369.00 matched (within 1%) $450-550 depending on vendor

So the set I have now is the Holley Terminator 76 # non-flow-matched. These are a Chinese injector offered from Holley. Other than being a little tricky to get to idle properly with my cam they work pretty well. But maybe I got lucky as far as the flow number tolerance goes.

What do you guys think? Is it worth it to pay the extra for flow matching?

 

The unknown is what is the tolerance between the highest and lowest flowing injector in the unmatched set? At your power output levels, will a lean running cyl cause harm before diagnostic methods like reading plugs and inspection cameras for piston color catch it? I know that the Holley Dominator can adjust individual cylinder injector output. But to know which and how much to adjust requires individual cylinder thermocouples on the headers. Your street machine isn't going to have the monitoring and logging capability to have the precision of individual cylinder adjustments.

So my choice to eliminate variables and hassle in tuning would be to get the matched set.

Another observation which I remember from the Syclone and Typhoon days: Big injectors have lousy idle characteristics because the IPW required at idle is so small. Idle quality is part of the justification for secondary injectors like the LT5 has, or the entire independent "drive injectors" system that Steve Morris developed for the Drag and Drive events he builds engines for. You mentioned idle quality because of your cam, but what is your current IPW at idle? If it's pretty short now, it is going to have to be even shorter with the 100#. Do you have the 'headroom' in the tune to go shorter IPW at idle? Something to think about.

Cheers

 

Good points. I don't have a way to tell individual flow rates per cylinder. I know the Siemens advertise +/- 6% out of the box. That seems a lot to me. Holley doesn't say on their non matched sets. So I think you're right. The best way forward is to pay extra and get a flow matched set.

As far as idle tuning with the injectors I have now, I was running a set of GM 43 pound flex fuel injectors before the nitrous. I can't remember the part number off the top of my head. But the Holley ECU had them in the drop down menu. So I just clicked on them and the car idled great. When I put the 76# Holley injectors in they also were already pre-loaded into the Holley software. But when I tried them it would stall sometimes. It was an easy fix by changing my IAC settings and adding a little timing under idle to compensate. So it wasn't a huge deal but did take an extra step. In Holley EFI you don't set injector pulse width per se. You set the injector off time. My minimum time is 1.2 msec. and at 12volt is at 0.86 msec. Looking at the data for the 100# injectors the 12volt msec is 0.99 and the same min of 1.2.

After doing a bit more reading it seems like people seem to like the larger Holley injectors. the 76, 100 and the 120's all seem to idle about the same. The 220's are a little different. Another thing I need to think about is fuel pressure. I could get the 120#'s and then lower the system pressure to 43.5psi. This would allow my fuel pump to flow more. That would give me a little more wiggle room in the overall fuel system. Or I could just say to hell with it it put in twin AEM pumps with the 100# injectors at 60psi.

Either way the car is good for the nitrous jets I have in it right now. I haven't even gotten the tank filled this year yet. But I know I'm going to be itching to swap in bigger jets soon. And all the online calculators are telling me those injectors are too small for any more spray.

 

Depends on your definition of matched. Matched used to mean they flow same at 100% duty cycle, balanced meaning they flow the same at all different pulse widths. This can make idle and driving in heavy traffic much more pleasant on a street driven car. Sometimes you can get lucky, but for me, Lady Luck must be a friend of my ex wife. I paid more for a balanced set of 35# Bosch ev14s from Deatschwerks. They came with all of the documentation that I needed for tuning. I think it was worth it.

 

I wish Holley was more specific. All they say is "Dynamic Flow Matched within 1%". I might look at Deatschwerks and see what they have that I can afford.

 

Dynamic flow matched means they're tested at various duty cycles and conditions. Static would be 1, typically full DC.

 

So after researching the crap out of injectors I think I finally came to a conclusion. The Holley Terminator injectors seem to work ok for most people. But they are just a Chinese injector that is made to Holley spec. I think since I'm asking a lot from an injector I need something a bit better. Being I'm asking them to flow enough for E85 and the extra fuel for up to a 200 shot of dry nitrous all in a street application, I kinda want something better. Deatschwerks has a LS3 style injector that will flow 98# at 43.5 psi. If I go this route this will allow me to lower the fuel pressure from 60 to 43.5psi. This will allow my Walbro 450 LPH pump to actually flow 450 LPH. So that would mean the pump I already have would easily be able to keep up with a bigger shot of nitrous

On sale these injectors are $600 for a matched set. But if it means that I can for sure keep my current fuel pump then it actually is a cheaper option. The internet is full of people who have had really good luck with Deatschwerks injectors. I've never used them before.

 

Can't you run the fuel pump at a lower speed with the holley too?

 

I could if I was using PWM for the pump but I'm not. I guess I could look into it though.

 

That could also help with drivability I'd think.

 

The Holley HP has 4 PWM outputs, B3 B10 B11 and B12 (I have a cheat book here that I've created on some of this stuff)... I would imagine the Termnator X does also.

The Walbro 450 uses a burshless motor and it's perfect for PWM... So basically you add an SSR and control the fuel volume.

People use the Holley Nitrous SSR, I'm using a much faster one. Also installed a flyback diode.

Advantage to using the PWM:

1. Fuel temp will be a lot cooler if you're not driving the higher capacity pump at full throttle all the time, from the heat generated from the pump and also not returning more of the hot fuel to the tank.
2. Less wear and tear in the components, less load on the electrical system
3. Without a PWM strategy, if you don't have a huge return line, and a bigger than say 255lph fuel pump, your FP will fluctuate and cause issues when you're fuel demand is low (deceleration, idle, cruising, etc.)

I posted details:
https://www.corvetteforum.com/forums...post1608031075

What it will NOT do is increase the fuel flow.

Regarding the original question about the matched set of injectors... I don't know if i trust it. There's a long story there, but the answer for me is that it's pretty cheap to get a Chinese injector flow bench. Fill it full of odorless mineral spirits, and flow 4 injectors at a time... take them through idle, high RPM, high flow, and if you see 1-2% difference, you can either replace or install a higher one to a cylinder that gets more flow, etc. Also with sequential injection and the Holley EFI you can trim each injector at low flow for idle and high flow for WFO.

The one thing that the cheap Chinese flow bench will not tell you is flow however, you can only do comparisons. The other problem is that the injectors actuating cause a lot of dynamics and the pressure gauge buzzez around at a multiple of the injector firing frequency, so I installed a cheap Toyota fuel pressure dampner on the flow bench and now it's rock steady. Also, same as your fuel rail, and injector that's a little further from th efuel inlet, will flow a little bit less, so swap them around sometimes to validate.

 

Honestly I never really thought about PWM for the fuel pump until you guys brought it up. I'll have to do some reading on how to set that up in the software. I would need to re-work some things on the fuel system to make it work. Right now I have -8AN feed and -6AN return. I have the flex sensor on the return line not the feed. I know you're supposed to have it on the feed. But at the moment I always have enough fuel in the return line to get a good reading. If I do a PWM SSR for the fuel pump it will reduce the amount of fuel in the return line. Not sure if that would effect the reading or not. But I don't really want to find out. So that would need moved to the feed line.

The more and more I read about injectors I've come to realize that it's not so much about flow matching or name brand as it is about the quality of the data they provide. In swapping injectors I really want to also lower my fuel pressure to 43.5psi. The Holley Terminator injectors only have data for 60psi. And in fact Holley recommends that the 100# and 120# be run at 60psi only. The Deatschwerks on the other hand give two data sheets with their injectors. One for 60psi and one for 43.5. They even provide their data in multiple formats depending on what ECU you are using. So I think I'm going to sell off the Holley's I have now and try the Deatschwerks.

 

I know deatschwerks is popular with the tuner guys. I'm running their fuel pump... mainly because I didn't want nor need the noise of a walbro. (Every person i know with one they work great mostly... few had bad ones, but the pumps are loud. The deatschwerks is quiet as stock which I like.)

I don't think their injectors are bad. They used to send custom bench data and offsets if you asked them and didn't charge for it. As in, they'd flow the set they're mailing you and give you whatever data you wanted. I don't know if they do that anymore.

 

Higher pressure equals better atomization. I wouldn't lower fuel pressure as a fix to make an injector fit your budget, especially in effort to make a power adder work properly.