550 cc injectors ??

[charliex]

Are people really running 550cc injectors ? this seems like way too much, thats like 400HP+, no cylinder wash ?

cheers

[mark]

yes, several guys have them installed and they seem to work fine. i put in 385s which are ok for my upgraded stock turbo and 18 psi, but they run a pretty high duty cycle at top end - wouldn't handle much higher of a fuel demand

[charliex]

you're running the same level boost as me, i talked to RC engineering and they said 550cc was way too much, same at the local turbo shop, they were thinking 200cc/250cc max, and at 550c it'd wash

colour me confused i'm hoping my hesitation from 0 to 5 PSI is the injectors. i'm installing an A/F meter in the downpipe to see what its doing there, RC recommended taking out the injectors and sending them over.

A set of RC injectors are less than half the price of the stock isuzus, i think they quoted me $200 an injector.


cheers mark

[Dave M]

I originally ordered 500s way back when, but RC goofed and sent me 550s. I've run them without any wash issues (no signs when the engine was torn down). When the car is properly tuned in a bit, I'll see what the duty cycle is to see if it is overkill at whatever HP figure I end up at.

[charliex]

maybe i should just order a set then. when i talked to the RC guy he seemed taken aback when i mentioned 550's.

I'm guessing between mark and dave, 450cc's would be more than adequate?

hmm they don't list 450 or 500, its either 370 or 550, i suppose they can change them to whatever though

[Ashaman]

I am also using them, I was scared not to as I WAS running 370cc units, and the duty cycle was getting too high. Since you aren't supposed to exceed 80% and I still have some room to explore, I installed the 550s (should be like 300hp, which isn't really overkill for some here).

200cc's is a joke; I have no idea why they would say something so absurd. That is like GEO METRO size! You would destroy your engine from running lean in very short order, as that number is good for only ~100 BHP on paper.

This really isn't complicated, increased power takes increased air & fuel. To deliver increased fuel, you will either need to raise base fuel pressure, or get larger injectors and a means of controlling them. There are online calculators everywhere, so I have no idea why anyone would tell you this...

Oh yeah, the stock units are 320, so that should tell you something about whoever recommended 200 or 250s!

There is no cylinder wash as you must also add a means of controlling them and it will comensate and allow whatever amount of fuel you specify...(I believe in my case .928ms gives 14.7:1 at idle).

[charliex]

yeah it makes me wonder, since i calculated around 340cc for stock with the injector calculator but its not something i felt competent enough to be sure about, learning as i go along.

there must be some reason though, they are a competent shop, maybe theres a different scale for a different injector or number of injectors, i find it hard to believe they'd be so far off, i really hope not

with RC eng saying the 550's were way overkill and for 400-500HP+ i figured it might have been a typo, best to check these things with people actually running them.

thanks for all the help chaps. i'll order the 550cc's, hopefully it'll help with my hesitation.

next step, getting the old ones out!

[Doc Fizzix]

charliex

I ordered mine from RC about four months ago and I think that I had some of the same concerns you are having so I bought the 330cc. They worked great, I got rid of my hesitation and the car drives and accelerates smooth!

After a ton of research I concluded that the 550cc were just too much over kill for the stock turbo unless you are planning to upgrade to a large turbo any time soon.

[charliex]

i do have a turbo @18 PSI with a larger impeller, 330 to 550 seems a lot, but then i'm just repeating what i've been told, so i'm heading to the dyno and having an a/f meter installed, i may send in my old injectors to RC just to see what they say about them.

cheers

[mark]

charlie, do you need a fuel controller? I just ordered a Haltech ECU, so will be looking to sell the Apexi fuel controller

[Ashaman]

Guys, it has nothing to do with the turbo you have but rather the fuel tables. If you have the stock ECU and nothing else, you have to stick with the stock injectors or you will run rich.

Even with the 370s installed (which is not a big difference) the car seemed fine. But when I put in the wideband I found out I was running off the scale rich under boost.

The ECU will of course 'know' it is rich via the O2 and try to comensate to some degree, but it is hardly a T-1000 luuhning computer Basically if the ECU reads the tables and pulses an injector for the specified duration the injector needs to be the same flow rate. If it is higher, it will run rich.

Now, a larger turbo may require larger injectors due to the increased pressure/flow if it is coming close to maxing the stock duty cycle. The point where this will happen varies, but do you really want to push it and find out?

So to recap:

Larger turbo/more horsepower
=need for larger injectors/increased fuel flow
=means of controlling them other than stock ECU.

One final point is that turbo/supercharged engines have a higher demand than their NA counterparts, make sure they know it is turbocharged. If they still know that and say 200cc is enough, run away...JMO!

[charliex]

i have a begi fuel pressure regulator as well as the larger turbo, so i've got the

larger turbo / more hp
begi fuel pressure regulator bypassing the ECU
= larger injectors ?

i also have alans maps but haven't used them, presumably not needing them with the begi, ut i was going to tackle that last.

[Ashaman]

In that case I do not know. Usually the FPR is used to raise base fuel pressure and get more headroom out of stock injectors. Since injectors are rated at say, 320cc at ~43 PSI, you can raise it to 50, 60 etc. and they will flow more as a result (again the online calculators can tell you how much). There can be problems from this as well however. Injectors can "lock" under excessive pressure, they also start to leak sometimes at the seams. Again, hard to say when/where this will happen.

I suppose you could buy larger injectors and lower the base pressure....I have never heard of anyone doing this but it makes sense...although a certain amount of pressure would be necessary for an optimal spray pattern I would think?

At any rate, you could play around with it with a wideband and see. I thought about going this route, but decided against it. To me it was more of a "getting by" approach with more potential pitfalls. One is the issues listed above, you are putting more strain on the fuel system, and it is hard to predict how it will perform. Another is can maintain a linear response via the FPR? For example, if you adjust it so you have a nice even idle with a stoich mix, what will happen as boost/revs increase? How accurate and consistent will it be under different conditions?

I do not know the answers to these questions. People do run this type of a setup, but I was not comfortable with it personally. Having said that, it might work just fine. If it does, it is sure a lot cheaper & easier than the alternavites! If it doesn't, it can surely be a heck of a lot more expensive and difficult.

[charliex]

thanks,

theres no evidence other than a guess that the injectors are the problem, i'm just trying to find the 0-5% hesitation, which is why more diagnostics are needed,

the car was running fine, and we dropped down to sea level quickly and problems appeared, had been running fantastically for 3 days at high altitude, i do have a flakey alternator thats being changed, so it could even just be a poor spark, but i'm also trying to learn as much as possible in the process so i can also say with some certainty 200/250cc is wrong as well as make sure i minimise my shop time, the A/F meter and the dyno runs with a fixed alternator should hoepfully get me on my way again, thanks very much again for everyones time (and patience )


today i found off dave simkin i get my new fuel tank, so that'll be first i guess.

[charliex]

this is a short run with elanscan ( with a engine off in the 3/4 time)

http://www.charliex.net/RUN2.zip

from what i can tell, it goes lean, and knocks around the same time i get the hesitation, which is presumably it retarding ?

higher octane gas (100) seems to help sometimes, not consistently.

[ESM]

It looks to me like you need to back off the advance a bit at high boost. The stock timing map is designed to avoid knock at a/f ratio of around 10 - since, I imagine, you'll be running leaner than that you should re-visit the timing side of things.

I agree with remarks above about injector size - the standard items flow 320cc/min and that is only adequate to deliver fuel up to 1 bar boost (and that's asuming you can go higher than 80% duty cycle).

[charliex]

alrighty thanks alan

[charliex]

ok so turns out to be really simple, the BEGI fuel regulator wasn't adjusted correctly, half a turn later and it runs pretty good now... they swore it was correct, but i took it to my elise mechanic and he took a spin in it and said, the fuels off, and sure enough it was

so i went through alternator, spark plugs + wires, fuel, didn't do the injectors though.

hoping to get it dyno'd soon though see what all this work has achieved.

thanks for everyones input.,

the damn things so low now i can't even put in the carwash