accel DFI

[tisilrad]

I recently acquired an Accel DFI fuel injection system, wondering if i should strip out the LH jetronic and replace it with the Accel? I would get rid of the MAF for one, and i could make adjustments with my laptop using the accel system....troubleshooting would be easier too. The only real hurdle i see is hooking up the idle air control. That will require some fabrication. I currently have a vacuum leak, guessing at the Idle air control hose under my intake..so major surgery is in the works...that would be the best time to incorporate the change....if i do i will have plenty of factory parts for sale..i have 2 of every major fail component for my S4...four coils, 2 LH controllers, 2 EZKs two ignition modules,...etc. Selling these would definitely fund the project if i could sell them. Whats your idea guys?

[XLR8928]

One wonders whether you will make any gains, that a shark tune may not exceed. I have L-jet on mine, and after careful analysis, and numbers crunching there is not a lot of low hanging fruit. A little gain in the exhaust area a little in the intake. Unless you are prepared to spend some significant $$, The intrepid Porsche engineers have done a pretty tidy job.

[Danglerb]

Flat out, I would not put an aftermarket fuel injection system on a 928. Waste of money, new major time sink hobby adjusting it.

[harborman]

Originally Posted by Danglerb

Flat out, I would not put an aftermarket fuel injection system on a 928. Waste of money, new major time sink hobby adjusting it.

Absolutely correct! Fix the original. Amazing how many want to butcher up a 928.

[tisilrad]

Well i have the system, and all the sensors so the $ input will be very small. The ability to troubleshoot the system will be a major advantage. It gets rid of the MAF and other expensive components which are 26 years old...As for the stock system..why do people think this is a great system..its almost 30 year old technology? I hear about it failing all the time and honestly it is an expensive system to repair or maintain? I have worked on cars for 20 years... and find for the most part they are all the same but the ability to diagnose and modify newer laptop accesible system shows a great advantage. As for a horsepower gain I really am not looking for any, the gain would be in an aftermarket supercharging or turbo system..that the stock LH controller was never designed to work with. I am not a fan of one shot reprogrammers like the sharktune system..any changes in the engine parameters require a reflash..seems silly.
In any event i am still up in the air...

[Alan in AZ]

Your rationale is kind of strange - full of holes...

If you don't need more power and have no plans to supercharge/turbocharge why change anything? Car is working OK today right?

You already have spares for the stock system, so yes its over 25 years old and some are failing - but not all - plenty are still going strong... so that means the MTBF is somewhere >25 years.

I wonder what it is for the Accel?

If you convert its clear you have a lot of work to do to optimize the system just to be close to the LH/EZK, installation is a hassle and when all is said and done you are back where you started.

If you stay stock there are folks who know the system, how many Accel based 928's do you suppose there are? how many experts to work on them? - It will just be you. Maybe you don't care because you plan to do it all - but it makes the car difficult to sell and reduces its value to others.

You say the LH doesn't have diagnostics - it does at multiple levels including the sharktuner, but for system fault debugging a Hammer or equiv is all you'd need. With a Shartktuner and PEMs you have instant real time updates - but for what you describe you don't need it anyway...

Everything I see says sell the Accel system and apply the money to something you actually need.

Alan

[tisilrad]

Well thats just it, i plan on boosting the engine in some way, where the stock MAF will be a handicap. I had an engine fire and the current wiring harness has been repaired but i am still uncomfortable with it. I have to debate the money end of it....if i sell the accel system i wont get much and i am back to the stock harness...if i decide to install the accel system i will be selling all of my unneeded components...at least the spares(ezk/LH/ignition modules/coils etc.). Interestingly it would not be too difficult to convert it back to stock if needed..maybe one days work? I honestly doubt I will ever sell the car, the engine fire was turned in on insurance and thus has a bad carfax report on that...so the cars value is not really a factor. Another factor is the availability of diagnostic equipment for my car..I dont have a "Hammer" to pull codes(though it is my understanding that doesnt really help a lot..according to the local porsche tech...not sure about him though.) I do have an O-scope to check for crank and cam sensor outputs but those are new anyhow...

[tisilrad]

so this is the engine after the fire...fuel line ruptured...

[Alan in AZ]

Wow - this story is evolving...

1) Get a new mechanic he sounds like an idiot

I'd certainly DUMP all ideas of starting with the Accel - you'd have to be totally ^%$#& nuts!

Get it working correctly in stock condition first - then consider the Accel - the only reason would be to allow for major engine mods in my opinion...

You'd also be nuts to attempt any engine mods before you verify what you have in stock condition. You know this already - don't go down that road to heartache...

Once its all back & working normally - then you can consider whatever changes you want.

Any other path leaves you not knowing what might be wrong.. something related to the fire or the Accell tuning or the engine mods... its just a nightmare. Get a baseline and start from there. It may seem like more work - but I guarantee you it actually isn't.

Stock Config working fine -> add the Accel in stock engine config & tune -> modify the engine & adapt the Accel. There is no other way that makes sense - you already know this...

Alan

[Danglerb]

+1 What Alan said, current mess is NOT a good reason to move from stock, just get a better mechanic.

[Niles]

Alan makes a great point about establishing a baseline, but I really want to see Tisilrad go forward with his plans. I like that adventuresome, hot rod spirit.

[Danglerb]

If one of the various aftermarket injection systems worked well, I would tend to agree, give it a shot, but ALL of them have issues, learning curves, and no long term history as a practical daily driver.

[tisilrad]

In all honestly it generally works well. I drove it to classes today, interstate and traffic and it ran flawlessly. The only major problem is a vacuum leak somewhere...i am guessing it is under the intake...probably the lower bearing in the intake butterfly valve? The top bearing in the intake has been replaced.I am idling high..about 900 RPM ...
The mechanic i spoke of has never touched my car...he talks a big game but all the so called porsche mechanics i have talked to either... A. know nothing about a 928, B.are just parts replacers who dont really know about automobile dynamics or c. both...
I rewired the car myself,(with help from Alan's write up about 928 electrics as well as factory wiring diagrams) it has aftermarket fue rails and regulator...but set to stock pressure with stock injectors, x-pipe, rear muffler delete. The stupid wide band O2 has quit... but before it did the car always ran stochiometric? Thats why i was always wondering why it acted like a vacuum leak. It has a rebuilt MAF, i have swapped LH controller with no change. It had Autothority chips but they have been removed due to idling at 1400 rpms! I think they exacerbated the already high idle. Almost all the sensors are new in the car and it now shows excellent drivability.
The one major problem i had was the central electrics...the car started to shut down when the head lights were switched on! Turned out to be corrosion on the terminals on the back of the central electric panel..especially the primary power wires to the number 30 terminals of the LH and EZK relays. Next is to run a new fused wire from the battery to the central electric. I guess this future project needs to be on the thread for common 928 fixes? My alternator is putting out 13.8 + volts but i have about 12 or so at the central electric...some high resistance somewhere there.
Anyhow i felt like i could eliminate some possible problems in the future with the accel DFI..but there is always something to do with a 20+ year old 928

[Alan in AZ]

Like I said - do it in a logicical sequence. Validate you have everything working right first. Move step by step with verification in between (e.g. drive it for while) change few variables at once so it doesn't get too confusing... Do what you want - but do it smart.

Not trying to stop you (if it makes sense...) but trying to save you grief down the road...

There is way more than enough grief to go around - Key is to become a real expert at avoiding it!

Alan