I am building a SuperRammed 406, and I need to choose a DFI system. I want something that is fairly straight-forward to tune, very reliable, and something that will be able to function even if a sensor fails. I am leaning towards the Speedpro, but if I cant buy it used, I'm not gonna be spending 2 grand for one new. Thanks guys!

 

I've run both the Accel/DFI system and the SpeedPro system. I had the Accel on a SuperRammed 383 for a couple of years, and now the SpeedPro on my SBC427. The Accel system is pretty good, just a littel 'rough around the edges' compared to the SpeedPro. but it's more than enough for a typical high-performance street engine. The SpeedPro I have is their fully optioned unit, Sequential with Wide-Band O2 and Individual Cylinder Fuel and Timing control. Most people, including myself, don't really need the Individual Cylinder Control, but I got a good price on it, paid $2400 for a brand-new kit. It woulda usually cost $3000. Anyway, you can get a new Bank-to-Bank SpeedPro with a Wide-Band O2 for about $1800 from several national tuners and retailers. I've even seen them advertised for a low as $1695 from some advertisers in 'Race Pages' and 'Fastest Street Car' magazines. The Bank system with a standard O2 goes for around $1400. I really like the Wide-BAnd O2, regardless of what system you get, consider the Wide BAnd option, it makes tuning so much easier and safer.

The new Accel DFI 7.0 looks pretty nice from the advertising. I was going to use it initially, but got tired of waiting on it. Supposedly, it's been available for a couple of weeks now, but I don't know anyone who has gotten their hands on it yet. It has the Wide Band as an option, and is probably a few hundred $$ cheaper than the SpeedPro (F.A.S.T.).

ZFrom what I've seen the Holly Commander 950 EFI unit looks pretty good for the price. I don't think it has a Wide BAnd O2 option though. Could be wrong, just never seen it mentioned in any of Holley's ad's or in any articles about it. But for the money, it looks like it's more than capable of fitting the bill, and the software looks pretty good, it's Window's based.

I would go with either the Accel or SpeedPro unit, or maybe the Holley system. The reason I say that is that you're going to find alot more support for the Accel or SpeedPro systems, and now possibly the Holley system, than you will for the Electromotive, Haltec, etc. There's just more market saturation. Accel has EMIC's all over the place, especially if your near a larger city. Most EFI shops tune the Accel's and/or the SpeedPro's. The same cannot always be said for the Electromotives and Haltec's.

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1982 Corvette
Tremec TKO
<A HREF="http://www.geocities.com/monty_williams/434specifications.html" TARGET=_blank>SBC 427 650hp/580tq
</A>

 

Awsome. Thanks for the help. Could you explain the difference between the regular and the wide-band O2 sensor? Anyone else?

 

A standard O2 sensor has a relatively narrow A/F range in which it is accurate. It's fine for a production car that runs at 14.7:1 A/F ratio all the time, except at WOT, for emissions and fuel economy reasons. The farther the A/F ratio moves away from 14.7:1, whether it be leaner or richer, the less accurate the O2 sensor readings are.

A Wide Band O2 is accurate from about 10.0:1 all the way to 20.0:1 or so. Therefore, you can use it to tune the car at all rpms and under all load conditions, including WOT.

Additonally, it makes tuning easier in that you can simply input targeted A/F ratio's at certain rpm/load points, and the ECM will enrich/enlean until it meets the target A/F ratio. When you have determined what the optimum A/F ratio is (based on performance, fuel economy, emissions, etc.), you can then see how much the ECM is adjsuting the pulse widths to achieve the target A/F ratio.

For instance, if you're tuning power at WOT, you know that typically normally aspirated engines make peak torque at about 12.7- 13.2 or so. If you were on a dyno or at the track, you could simply try each one of those A/F ratio's and see which one resulted in the best torque or lowest ET.

After determining the optimum A/F ratio, you simply adjust the pulsewidths to achieve zero trim, so that it isn't relying on the O2 sensor to enrich or enlean the tune.

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1982 Corvette
Tremec TKO
<A HREF="http://www.geocities.com/monty_williams/434specifications.html" TARGET=_blank>SBC 427 650hp/580tq
</A>

[This message has been edited by Monty (edited August 06, 2001).]

 

Thanks for the help. Which system do you think would be more straightforward when doing those adjustments?

 

It all boils down to the software if you're talking about ease/straightforwardness of tuning it.

The new versions of the Accel/DFI, SpeedPro, and Holley systems are Window's based, so it's going to be more straightforward and intuitive for most people, since it's largely drop-down menu and point/click based. Either brand of software is going to have is own learning curve, and all of them are basically similar.

I'd buy the system based on whether or not is meets your needs. Do you need/want: Sequential vs. Bank-to-bank vs. Batch-Fire; Regular O2 vs. Wide-Band O2; etc.

Also, consider service after the point of sale. More than likely, you're going to want to either get someone to tune it on a chassis dyno, or at least give you some pointers. If you have a local 'speed shop' or machine shop you're confortable with, their assitance and advice is invaluable until you figure it out.

I haven't heard anything from your comments which leads me to believe you need a high-end unit like the SpeedPro's. I would suggest the Holley unit. The software appears to be intuitive and user-friendly, and it has all of the basic features you'll need. If you want the Wide-Band 02, then go for the SpeedPro.

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1982 Corvette
Tremec TKO
<A HREF="http://www.geocities.com/monty_williams" TARGET=_blank>SBC 427 650hp/580tq
</A>

 

Well, I want soemthing that is going to be able to givge me the most flexability in tuning so I can squeeze every last bit of HP out of this engine that I can. The car needs to be very reliable, as it is my daily driver. I would like some sort of data-loging feature that allows me to analyze my runs, and a live engine metrics screen to see exactly what is going on in there. Will the Holley do this for me? I didnt get too much from their online documentation.

 

Excuse my ignorance, but would someone be able to explain EXACTLY what it is we are talking about?

 

It's an aftermarket alternative to burning your own eprom for the stock GM ECM.

 

Hey Monty, I was talking with a guy who works for Holley (on another website) and the 950 is capable of wideband O2 option.

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Edited portion:

I just went back to the site I had coorespondence with, and the 950 does NOT come with the wideband O2 option, sorry about that.

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Like you said, the price is very attractive...I think Summit has the GM TPI kit for less than $800.00.

One thing about the Holley, is no codes are given for out of tolerance..i/e no code 44, etc....in order to see how the engine is performing, you monitor all fuctions at once...kinda like a scan tool, with no code reader.

GTA, what's being discused is user control of the EFI system...i/e instead of burning a prom to try and get the most out of what you have, you interface your laptop to the new ECM and adjust/tune your engine as you see fit.

[This message has been edited by 8Mike9 (edited August 06, 2001).]

 

Scott,

All of the systems have data-logging features. Typically the data-logging can be triggered by either the user making a keystroke (hitting the space bar) or by exceeding some user-defined parameter, like more than a % of TPS.

All of the major systems are reliable. I've never had a problem with any of them.

While it is true that the aftermarket systems don't utilize a 'check engine light' to flash codes, you still have excellent trouble shooting capabilities. Rather than wath some flashing lights to get a code, you see the actual parameters of the various sensors. In my opinion, this is alot easier. You get to see the acual data, not how it is interpreted by the ECM via trouble codes. You basically get to see the actual source of any potential problems.

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1982 Corvette
Tremec TKO
<A HREF="http://www.geocities.com/monty_williams" TARGET=_blank>SBC 427 650hp/580tq
</A>