fast951

I was wondering if anyone ever used a PiggyBack system on a 928.. If so, what feature did you like, or would like to have on the system. I'm evaluating a system with great results (on a 951). The system I'm working with handles Fuel, Timing and can DataLog to your PC, nice user interface and stores multiple profiles that can be switched externally or via software.

I'm thinking of adapting the same system to my 87 S4.

I would like to get some opinions...

Barry Johnson

I've heard great things about the Perfect Power SMT-5 for the 928s. Their is a new one, the SMT-6, but its software is not going to be as bug free as the 5, and it really won't do anything special over the 5 as far as what we'd use. <a href="http://www.perfectpower.com/products/uni5.asp" target="_blank">Perfect Power SMT-5</a> There is the link to it. I'd really suggest going with that. It seems like the best way to go for the money, and Louie Ott (maker of the famous Ott X-crossover and other goodies) sells them with some 928 specific instructions I believe. I can get a hold of him if you want. I think the unit is about $250. So thats cheaper than getting an AFPR and ARM-1.

BJ

ViribusUnits

I have a question.

What are the advantages/disadvantags of useing a piggy back system?

I know it's not suppost to be as good a a new stand alown system, but I don't know why, and in what ways. I also know piggy backs are suppost to be better than the stock system, but again, why and in what ways?

Thanks

Barry Johnson

The advantages of the piggy back are for one, the ability to toy with the settings, and not permanently modify your car. You can advance or retard timing, play with the fuel maps for different fuel pressures at RPMs, and it will also have extra stuff for running forced induction or nitrous, like an extra injector control. You can tune it on your laptop and see real time A/F ratios and have 2 different ECU settings that you can switch while you drive, so basically run one for economy, and then switch on your performance one, but thats if you leave the laptop in the car. The benefit of this over a stand alone is that you don't start from scratch on the map settings and everything else. You have a stock baseline to go off of provided by your current ECU. However running the stand alone definately allows more tunability as for example, the perfect power PRS8, has a throttle position sensor for tuning at partial throttle, and running a MAP instead of a MAF, wasted spark setups, all that cool stuff. The stand alones are probably 4x the cost though, but still cheaper than buying a new LH and EZK if you have an '87+. My LH just ate it, but I'm going to jumper the fuel pump relay (yeah not the safest but it wont hurt anything unless I leave the key on for a long time without the engine running), and then do all the tuning I'd really need with the SMT-5. I've REALLY considered buying the PRS, but I want to do a few other things to the car at the same time, so I really can't afford to do it, otherwise I would, and I'd also be on the road right now. Hope this helps! If you have any other questions, or you wanna get one, let me know and I'll do whatever I can.

BJ

John Veninger

[quote] but I'm going to jumper the fuel pump relay (yeah not the safest but it wont hurt anything unless I leave the key on for a long time without the engine running), <hr></blockquote>

Just a word of caution. This works fine as a temp. fix. Not really good if you get in an accident and don't have the ability to turn the key off.

Jack '84 928s

The 951 guys use the SDS its $1200 and MAP base. <a href="http://www.sdsefi.com" target="_blank">www.sdsefi.com</a> supposed to be as easy as hooking up a car stero.

CarreraFour

Rather than give you my personal experience with the Piggy-back computer on the 928 (all good by the way) it is easier to simply put you in touch with Louie "The 928 Professor" Ott directly.

I don't believe I have ever met anyone to date in this forum that has disassembled, reassembled, tested, re-tested, inststalled, questioned, answered, dynoed, duct taped knuckles on piggy-back computers on 928's more than Louie!

Trust me this is the man to talk to about that topic.

He will respond to your email if you write him at louisott@cs.com <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />