johne

Well it looks like I’m maxing out my fuel injectors with my new T04e and so I’m going to pick up some new ones. I am looking at the 75lb Delphi Injectors from www.racetronix.com. They are $240 plus shipping for 4.

Justifications:
I did a search of the archives and racetronix seemed to be the most common place to buy injectors from.
Also I picked the 75lb size because it sounds like 83lb injectors give a little bit rougher idle so I figure I will go with the next size down.
Also Danno says that Delphi injectors give a much better spray pattern which helps give a smooth idle.

So I am curious if anyone has any other opinions. I hate it when I make a purchase and then a few weeks later someone post something saying that my decision was all wrong. Grrrrrr. So if anyone disagrees with any of my justifications, please speak up.

Thanks everyone,
John

TRWright

What injectors are you maxing out? Do you still have the stock fuel pump?

johne

Thanks for the reply Ted,
I have newish stock fuel injectors and I'm pretty sure it's a stock fuel pump (I have found a couple undisclosed upgrades from the previous owner so I'm not sure).

Here’s the long story:
I am tuning my own chips and I am upping the boost pressure in increments, once I got up to ~12 psi of boost I started lean in the higher RPMS no matter how much fuel I added. I had the WOT fuel enrichment tables at 255 above 5500 RPM and my AFR was still going lean. I already have an AFPR (adjustable fuel pressure regulator for the noobs) so I upped my fuel pressure to around 3 bar and was able to dial back in the AFR. The surprising part though was that increasing the fuel pressure did not add fuel evenly across the board. Why? I don't know, but I don't really feel like researching it that much. Seeing as I should be able to make 350+ rwhp with this turbo I'm going to need bigger injectors anyway so instead of fooling around with the fuel pressure I'm just going to go ahead and upgrade the injectors. I also have heard that the stock fuel pump can only flow enough fuel for 350ish rwhp at 3 bar, but at 2.5 bar it should be able to flow closer to 400ish rwhp. I looked at a fuel injector calculator online at http://www.stealth316.com/2-air-fuel-flow.htm and the 75lb injectors should be able to support 455 crank hp at 90% duty cycle at 2.5 bar. If I go with the larger 83lb injectors sure I could support 503 crank hp but my turbo won’t do that on pump fuel and I have heard that 83lb injectors give a slightly rough idle, which is not desirable.

So in summation, with the 75lb injectors I believe I can support all the hp my turbo will make at 2.5 bar of fuel pressure which will allow me to keep the stock fuel pump without having a lumpy idle.

Short version:
Read the above paragraphs really fast.

As always comments or questions are more than welcome.

John

fast951

If the software is programmed correctly you can run the 83# and notice no difference from stock. This weekend we will be trying the 95# injectors...

Ski

John, we're running 55# ones on the track car, with Vitesse race chips, LR III MAF, Kokeln club turbo - slightly modified, and Mafterburner piggyback and have no problems at all; we can dial the car in a bit lean, a bit rich...17 psi was 351/347 respectively, fuel pressure was 46# static. What sort of boost do you plan on running?

ibkevin

When I read throught he archives before buying I got the inpression Delphi were not well liked, so I went with Siemens.

johne

John(Fast951),
While I would love to figure out how your doing the semi-sequential thing, I don’t foresee my chip tuning getting that advanced any time soon. If you would like to share with me how to modify my chips I am allll ears. :biggrin: I know that you and TT are very skill at programming the Motronic, I’m just trying to get mine tuned reasonably well though.

Ski,
I’m trying to run as much boost as possible of course, well actually I plan on making 2 fuel maps. One for 87 octane at around 12 psi of boost for road trips, and another for premium at17-18 psi of boost for around town and fun.
I agree that I could probably get 55’s to work by upping the fuel pressure but 55-85’s are all the same price and by going larger it shouldn’t limit my cars future potential and hopefully I can get away with using the stock fuel pump for a while longer.

As always comments or questions are more than welcome.

John

johne

Kevin,
Really? I hadn’t caught that, what pro’s and con’s did you turn up?

Thanks,
John

mark944turbo

An obvious question, but are you sure you are modifying the correct full throttle table? There are 3 sets of them and if you are modifying only one of them you could be effecting nothing and only noticing differences in your head. What I do is change all the pointers to point to one table so I know I am making results.

Other than that, I agree, you need new injectors.

Sounds like you are making progress anyway !

hally

Hi John,
whats your approach to timing, are you currently using timing maps from a k26 chip while you tune the fuel maps?
keep us posted on how you go, interesting stuff.

Charlie944

I have the 75# Delphi's from Racetronix and I have had zero problems. I had head that the high flow Siemens produce a 'garden hose' stream of fuel through a radius rod design, while the Delphis with their 6-hole diffuser disc produce a nice cone shape hence better atomization promoting a better more complete combustion. I did contact Danno and he advised me to use a 3.0BAR Fuel Pressure Regulator with the 75# Delphis. The only thing I have heard is that the Siemens have better flow linearity than the Delphis, but I have had no first hand experience comparing the two. I say go with the Delphis. Here is some more great information from Russ Collins of R.C. Engineering: http://www.suprasonic.org/public_htm...rs/RCtech.html
Hope this helps!

fast951

Siemmens are fine, we have 83# on a 944NA.. Once you go to larger injectors, there are many things that must be taken care of in order to get clean idle and crisp respoonse.

ehall

^^^^^^^^^^^^^ Like?

NZ951

Wont 55lb injectors be big enough? (just a wee joke there)

I have Siemens 83lb, they work fine, I would note however that if I was going smaller, I would prefer Delphi as they have a wider angle spray pattern.

johne

Thanks everyone for the added input!

Mark,
Yep I’m working on the correct table, I’m actually editing the part throttle table while I’m at it since my configuration is wayyyyy different than stock. Thanks for the reality check though, I have edited the wrong table before and as you say, you “imagine” that the changes are sort of happening. Thanks for continuing to look out for me, you da man.

Hally,
Good question! I started off using stock ignition maps, now I’m using Weltmiester ignition maps, which look a little more aggressive. My technique thus far has been to listen for knock with my ears, and since I haven’t heard any yet then I must be ok right? Yeah I know, tuning the timing is very important. I haven’t yet decided how I’m going to go about it. I’m all ears if someone has some ideas though.

Charlie,
Awesome feedback, so you don’t have any idle issues at all? Your sig doesn’t say whose chips your using or how your handling tuning, mind sharing? Also thanks for the link; Russ does share some interesting info.

John (fast951),
You mention crisp response, I assume you are referring to adjusting the acceleration enrichment. If so I would love to know where that variable is located within the chips. If you don’t want to post it on the boards feel free to PM me. Also I *finally* found that wastegate that has a broke stud if you still want it.

NZ,
A couple questions if you don’t mind:
How does your idle compare to stock? Is it 100% as smooth or maybe just 80%? Also, are you still using the DME/KLR, or did you move up to standalone. Lastly is there any particular reason that you would like to have the cone spray pattern of the Delphi’s or does it just seem like it is preferable to you.

Thanks for all the comments everyone, I am feeling much more confident in my decision. Of course any other opinions are still more than welcome, positive or negative.

-John