Tweecer RT question

[Brett B]

I'll be putting a cartech outlaw turbo kit with a 76mm turbo on a R302 block, in the near future. I'm obviously going to need some big fuel injectors injectors. I want to make around 800 hp in a driveable, stealthy combination. Just like the last coupe plus 300 hp :)

Whats the largest size fuel injector the Tweecer will drive? And another idea I have but havent researched... Chris Johnson used to sell injectors that flowed alot... like 30 lbs would do 50 and 42 would flow like 70 pound injectors.. anyone know what I'm talking about?

[Saleen91]

The TwEECer only modifies the factory EEC calibration data. It is not an injector driver. Your factory EEC does that, and it is setup run high impedence injectors. The largest high imp injectors are 50-55#. The injectors you're thinking of from JMS are 30# (rated at 47# when drilled) & 36# (rated at 77# when drilled) injectors that have been drilled out. I ran a set of his 77's (drilled out 36's) for a while without a problem. The don't flow a true 77 IMO, and are a little tricky to tune with for drivability. Nothing hard, it just takes some trial and error to find out what the car likes and dislikes with those injectors.

I've since upgraded to low imp 83's and I'm using an external low impedance injector driver that Pro-M used to make. There's also another company that makes an external box, called Acceleronics IIRC. Your other option is to find somebody who can modify your EEC to run low imp injectors. Alternative Auto and Mike Wesley USED TO do this. I don't know if they still do, but it's worth checking into.

Bottom line, I ran the 77's until I stumbled across one of these Pro-M boxes and could run true low impedance injectors. Having switched to similar sized true low imp injectors I've notice a smoother idle and I've got a LOT more control over my flow at WOT. For example, I went to a dyno w/ the 77's and then a couple of monts later with the 83's...and a new MAF but that's another story. I wound up leaning out my WOT fuel between 25-35% at WOT with the new injectors.

The "cool" factor about using a TwEECer is that you can dial in a mismatched combo with respect to your injectors and MAF. For example, I ran those 77# injectors with a Pro-M MAF that was calibrated for 36# injectors. The problem you potentially face doing that is that you run the risk of max'ing out your MAF as far as the amount of air it can REGISTER. It's not a size issue...75mm vs 80mm vs 83mm. It's a calibration issue in the electronics. With a TwEECer RT you can use the datalogging to find out how close you are, or if you are max'ing out your MAF. But I'll save that for a later post.

[Brett B]

so I need a factory computer, the TwEECer, and low-imp driver, and then just buy some 77-83# injectors?

Who makes the best low-imp driver box and is there any issues that are involved? Would it be bette/ cheaper to go with DFI or a FAST system in the long run?

thanks

[Saleen91]

Do you not have a factory EEC right now?

If you're starting from scratch, and KNOW that you'll need injectors that flow MORE THAN 50#, then you'd probably be cheaper off with DFI or FAST as they can run low imp injectors.

The only low imp injector drive I have experience with is the one that Pro-M used to make. It's a simply plug and play box.

Also, the 77's are just 36# injectors that have been drilled out.. They are high impedence.

[Blue91]

I run his old 77's with a stock a9l eec and a chip. :-)

[Brett B]

well shit, i bought an old laptop and was all ready and excited to get a TwEECer for my TT coupe, beforeit got totalled.

Its just hard to drop $2,000 on a new DFI or fast system :(

New question.. what sucks about the generation 6 DFI versuses the newest (7 version). Anything I shoud look for in particular between the different systems?>

[Saleen91]

I'm DFI illiterate.. :(

[Redsnk95]

Get the Gen 7 if possible. The Gen 7 is much much much more user friendly as compared to the Gen 6 and there really isn't much support out there for the Gen 6 anymore. You can find the link to download the demo program on my board in the Accel forum.

Troy

[Alex in Houston]

Have you looked into the AEM management unit? Tons of features, user friendly as hell and just a bit over 1 grand in price. You use your existing wiring harness and sensors so no need to rewire the car with a bunch of GM sensors. It can run as a MA or SD set up and supports low OHM injectors. It's what I plan to run in the not too distant future.

[Brett B]

as far as my research has shown, the AEM is NOT low-imp ready and will require an outside driver box to run the larger injecters. Other than that it looks like quite an awesome box at a resonable price, but once you add the low imp driver and a *decent wide band your right back into a Gen 7 DFI system which has been proven a thousand times to work on HUGE hp cars :)

[Saleen91]

For what you want to do, I'd say it comes down to the Gen 7 DFI or FAST.

[Redsnk95]

Call Fuel Injection Specialits in San Antonio if you want the Gen 7...call Mike Murillo if you want the FAST.

Troy

[Saleen91]

Actually, Conley's Performance here in Houston is an authorized DFI dealer/tuner. They just got a new Mustang Dyno as well to do all of their DFI tuning on site.

[rotax]

With one of the dfi systems, FAST or GEN7, is there a way to have some kind of real time display like on a PMS system with a palm?

[itlkick]

I know I am late in this discussion but I run the TwEECer RT with the external Pro-M injector driver and 83lb injectors. I love this combination. I have tuned many different systems including Accel DFI, Holley, and the TwEECer/EEC-Tuner. The only bad part (in my opinion) with the Tweecer is that the manual is virtually non-existant so you have to learn by yourself. Once you learn it everything is great.

I am going to make a statement that may piss some people off (it is amazing that people get upset about this). I DO NOT LIKE speed density systems. The DFI is speed density. I have heard they do have options for reading a MAF but it does not work like a true Mass Air system (this is what I have been told). You said you wanted to build a stealthy street driveable system that makes tons of power. In my opinion you NEED mass air to do that.

The reason is a speed density system calculates load based on the vacuum or boost in the intake plenum. Using this information with RPM, throttle position, etc. it can calculate the load and compensate for driving conditions. The problem is when you make more power you generate less vacuum at idle. This makes the resolution of your normal drive conditions very small. With Mass Air the computer knows how much air is entering the engine. It uses this information along with RPM, throttle position, etc. to calculate load. Since air flow is being measured you can run no idle vacuum and still have great driveability.

In either system when you make a lot of power your resolution is decreased. With Mass Air you have 0-5 volts to represent the air flow from idle to WOT max RPM. With Speed Density you have 0-5 volts to represent 32 inches of vacuum to the maximum rating of boost. If you run > 14.7 lbs of boost you need a 3 bar sensor. In either you loose the fine resolution capability of a stock system.

[rotax]

So were doomed?

Looks like we have to deal with Pro-M to have a good MAF....yeah right.
I had a 80mm cal'for 50's and it was running perfect, except i was maxint the injectors at 5000 rpm's
I got a 80mm MAF cal'd for 72's and look at what the flow sheet error look like vs the 50cal.

both are Pro-M 80mm

flow pts 50 72

Error in %
1 1.4 -0.8
2 0.9 -0.2
3 1.7 1.2
4 2.3 3.8
5 2.8 9.8
6 2.5 15.1
7 5.2 29.0
8 6.0 51.3
9 10.5 66.6

No wonders why it runs like crap, part throttle and wot.