1000cc injectors and EMS

[turbogate]

Quick question guys. I am getting an AEM EMS soon and currently have an MKIV TT fuel pump and 550cc injectors. At the moment, I dont need bigger injectors yet, but will for my future plans. Will I have any problems in the mean time with 1000cc, MKIV fuel pump, AFPR with my current set-up(see sig)? Will the AEM EMS control them without any idle issues and decent cruising fuel economy?

Thanks

 

[gixxer750]

It's going to take some work to get a good idle, but it's doable....

 

[aljordan]

The EMS seems to idle ANYTHING.

However, you'll run out of pump with 1k injectors and only a single mk4 pump.

 

[turbogate]

The EMS seems to idle ANYTHING.

However, you'll run out of pump with 1k injectors and only a single mk4 pump.

Even at moderate boost (+-19psi T04 60-1) and +-43psi fuel pressure(static)?

Thanks

 

[gixxer750]

It's a matter of scaling the microbit sec correctly to get an idle and still have fuel at higher boost. Sometimes its a pain.

 

[turbogate]

It's a matter of scaling the microbit sec correctly to get an idle and still have fuel at higher boost. Sometimes its a pain.

Thanks guys.

gixxer, did you ever fix the issues you were having with you EMS, the revving problem?

 

[aljordan]

Even at moderate boost (+-19psi T04 60-1) and +-43psi fuel pressure(static)?

Thanks

Since you're not going to be anywhere near close enough to maxing out 1k cc injectors with a measly 60-1 at 20 psi, I'll do the math to show how to figure out if a pump will be enough to feed injectors at any given pressure.

1000cc injectors x 6 = 6000cc of wide open flow.

base fuel pressure of 43 psi + 20psi of boost = 63 psi actual at the fuel rail.

Below is a chart Dave Henry did many years ago with a few different pumps. I've since seen more accurate numbers with fresh pumps, but this will work for my expample.

6000CC x .015783 = 95.238gph (from www.rceng.com tech article)

95 gallons per hour crosses the mk4 pump line at.. never. Again, this is 100% duty on 1k cc injectors. Say we use 50% duty cycle as our max. This makes gives us 48gph. This would put our mk4 pump falling off at 48ish psi of pressure. That would be a static of 43 + 5psi of boost.

Again, I've seen updated numbers for the walbro and mk4 pump done by RC engineering on their pump dyno. I would take those numbers over Dave's. I didn't want to dig more than 15 minutes on pump numbers, so one will have to find that updated information if they decide to do what I've done above. Also, rarely do people run 43 psi of static fuel pressure.

 

[dbsupra90]

the blue line is supposed to be hi press walbro. man, its been ages since ive seen that graph!

 

[Nomad707]

sorry to ask, but i have an on topic question to ask..

Are mkiv fuel pumps the same for turbo/non turbo models?

 

[turbogate]

Also, rarely do people run 43 psi of static fuel pressure.

Thanks for the info. So does that mean I should be ok for now? lol, you lost me for a little bit. I meant to say 43psi base fuel pressure without vacuum line attached.

sorry to ask, but i have an on topic question to ask..

Are mkiv fuel pumps the same for turbo/non turbo models?

I dont think they are the same.

 

[aljordan]

Thanks for the info. So does that mean I should be ok for now? lol, you lost me for a little bit. I meant to say 43psi base fuel pressure without vacuum line attached.

If you run 43psi static (no vaccum), 1000cc injectors, a single mk4 pump, and only run 6 psi of boost, you'll be fine. The most a mk4 pump will do is 49psi at the rail. That's 43 static and 6 psi of boost, or 33 static and 16psi of boost. The final pressure has to be 49psi or less.

Truely, you're running an AEM, so you an run static pressures of 33 psi and run 16psi of boost. The pump should be able to do that, but not much more.

Pumps create flow and when they are restricted, they create pressure. You adjusting fuel pressure, is that restriction. When they get restricted, they start to flow less and less. The more restriction, the less flow.

People say you can run about 550rwhp on a single mk4 or walbro pump. That's at the edge... the very edge. Too close for a street car if you ask me. As long as you're under that power level, it *should* work.

This is one reason why I've been at 500rwhp for 5 years. Quite the PITA to add dual pumps to the small mk3 hanger and be able to squeeze them into that small opening. After doing it on a friend's car, I wanted to sell mine.

Why not opt for some 680 injectors. Those would be a better match for your needs. In fact, that should be about all the injector you'd need on that turbo. You'll even have injector to spare.

 

[turbogate]

Why not opt for some 680 injectors. Those would be a better match for your needs. In fact, that should be about all the injector you'd need on that turbo. You'll even have injector to spare.

I hear you, it's just that I will not be running this turbo for long. I'm getting the AEM this week or early next and there are some good injector deals floating around. I figured if it wouldn't be a mission to tune 1000cc with my current fuel supporting mods, I would have jumped on those deals. I guess I'll keep my 550s for now and squeeze as much as I can from them safely. When I slap the bigger turbo, I'll work on the fuel system as well.

Thanks for the good info

 

[yaitsme]

Sounds like you're planning to write the EMS calibration yourself? If so, then you must be confident enough in your ability to give it a shot. If you're planning to hire a pro to setup your AEM, then you oughta talk to them before buying those 1000cc's.

I started out with RC1000's & an AEM. Had an AEM certified pro setting up the EMS, and although he was confident in the beginning - he couldn't dial the injectors low enough to idle worth a shit. Then we brought in a semi-pro, with much MkIV and AEM experience ... he couldn't pull it off either. I'm now running RC750's - still plenty "over & above" for any future plans, and they idle.

(Just for reference - and I'm gonna get my terminology all screwed up here, but - the injector calibration table allowed the duty cycle to be set using values of 1-255. Setting the 1000cc's to "3" at idle was just too damn rich & a setting of "2" was too lean.)


... just my $.02 ... pro-rate that considering my lack of experience.

 

[aljordan]

yaitsme.. it's likely due to the way the AEM fires the injectors. Rather than batch firing them, it fires each injector once per revolution. IIRC, the mk4 aem batch fires the injectors and those guys idle 1200cc injectors without a problem.

The *mk3* aem ems is a hack. Stock is batch fire, and aem fires all injectors once per revolution. That's unsavory.

 

[turbogate]

Sounds like you're planning to write the EMS calibration yourself? If so, then you must be confident enough in your ability to give it a shot. If you're planning to hire a pro to setup your AEM, then you oughta talk to them before buying those 1000cc's.

It's actually the other way around, lol. I have a profesional also certified AEM tuner tuning my car for almost nothing $ wise (I did'nt have the chance to ask him about the 1000cc yet) So I figured since I would need bigger injectors later on, I might as well have him tune the car with them. But like you said, 750s will probably be more than I'll ever need, I might as well be patient and get the bigger injectors when I really need them.

 

[gixxer750]

(Just for reference - and I'm gonna get my terminology all screwed up here, but - the injector calibration table allowed the duty cycle to be set using values of 1-255. Setting the 1000cc's to "3" at idle was just too damn rich & a setting of "2" was too lean.)

The problem in that situation wasn't your injectors. It was improper setting of the microbit sec to allow enough resolution to allow a good idle AND plenty of fuel at top end. The proper way that this should be set is to allow between 15-30 in the idle area(raw values) and around 220-240 @ highest load/boost pressure