I've done a ton of research, and I've got a great idea of where I want to go, and how I can get there, but I'd like some opinions from some people that have been there before because this stuff is expensive! Here's what I'm planning: Twin turbo small block, running approximately 8:1 compression. This car is going to be used mostly on the street, and I'm planning on running 15-20 psi usually (depends what I can get away with on pump gas.) I'm going with fuel injection and distributorless ignition. I plan to build the engine to be able to withstand approximately 28 psi max -- and build the fuel/ignition systems to be able to compensate for these boost pressures as well. I'm going turbo because then I can run 15-20 psi typically, then fill up with some higher octane and crank the boost. Because I'm building this to handle these two distinct operating 'modes' so to speak -- being able to switch the ecm from one set of operating parameters to another fairly quickly and easily is a big requirement. I like the idea of real time programmability via a laptop -- but in all honesty, after the initial tuning period it probably isn't necessary as long as the two sets of parameters can be switched back and forth easily. I've been leaning heavily toward the Electromotive TEC II system because it integrates DIS, EFI, and utilizes real time programmability -- however it costs big $$$ which is a drawback. What are your opinions -- can I accomplish my goals with a GM ECM/PCM or do I need to go aftermarket? Thanks.

One idea is to use an ECM with a replaceable eprom (like older GM). You could build a simple adapter and use a larger eprom. Connect the 'extra' address pins on the larger eprom to dip-switches. Then you burn different calibrations in the prom and select wich one to activate with the dip-switches.

If the ECM uses a 4k eprom, and you build an adapter for a 16k eprom you will have two extra address pins (and two dip switches).
That gives you four different combinations.

off off - First calibration
off on - Second calibration
on off - Third calibration
on on - Fourth calibration

You can use as large eprom as you like if you need more calibrations. Just build the eprom adapter for whatever size you want to use.

This will work on some GM ECM and some aftermarket.



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Jonas Bylund

Might research the syclones a bit more before you think of 28 PSI.
With a 5 bolt chamber bolt patern for the headgasket that makes the bottom end the weak spot.

I've run my GN up to 28 PSI, and it's a real fine edge to stay there. Race gas is another story.

The syclone ecm is tunable for 8 cylinder applications.

There is even a 3 bar MAP version of the calibration available.

Unless your real familiar with turbos and big HP you need to do about a 100 tons of research. No flame meant, just 28 PSI is serious HP country.....

I routinely run 20 PSI on my GN using a somwhat stock ecm. But others are running about that with stock ones, granted different chips.

Grumpy -- the 28 psi is where the post comes from. I've done my share of research

I plan to run 8:1 compression and about 15-20 psi on regular gas -- with one tuning 'profile.' Then about 28 psi on av-gas with another 'profile.' I plan to be able to tune it for each of those specific scenarios, and (hopefully) be able to switch back and forth with ease. Also, I plan on building the engine to hold up to 1000 hp. Not that I see myself as making quite that much -- but I don't see that I will have a problem with durability if I build it with this use in mind.

To even approach 1,000 HP means 60#/hr injectors, and nothing in that range is saturated, so your answer is you have to go aftermarket, or with a external driver board, but for the price of the injector driver board might as well use the aftermarket ecm.
Trying to run 60s also means your going to need SEFI to get a decent idle.
So you'll be needing one of the MSD distributors with the cam sych signal. If you going that far, and want to have a decent ignition (for a 1,000 HP), then sriously think of the FUEL eDIST and going coil near plug.

Research about the injector sizing would have answered the initial guestion right away <g>..

All I have to say is this



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Check out my Hompage,or the beginnings of one.355 dynoed at 400HP at 5800RPM & 410LBFT of TQ,on Motorhttp://www.procharged89z.cz28.com/index.html

Damn. Between the two of you. I'm not running 60# (or more) injectors. For a street car that would be totally unacceptable as far as idle is concerned. I'll most likely be running two sets of injectors. One set will operate under normal conditions -- the next set when necessary in high boost situations. There's aftermarket ecm's with that capability (in case you didn't know.) I have done no research on factory ecm's thus far -- but i hear comments every now and then about how wonderful and adaptable the factory ecm's are. i'll also be running distributorless ignition, which, with a few upgrades (if necessary) should be up to the task. there's absolutely no reason that i (or you guys) should be worried about me building an engine specifically for my goals -- and running 20 psi on pump gas and approx. 28 psi on 105-110 octane. by the same token, if you think that my goal of tuning the ecm specifically for these two octane/boost level configurations and switching between the two tuning configurations easily is far fetched -- then what the hell is all of this technology really good for???? i'm not attempting to sound like an engineer because i'm not one. however, i do know and understand my fair share about this, and combined with the fact that my father has been building racing engines for the past 30 years -- i think that our combined knowledge/experience will prove able to accomplish these goals with little to no major complications. in case i need to remind you -- my original post was only about one thing -- aftermarket vs. oem ecm/pcm's. which do you prefer -- and why? i'm attempting to gain information here.

one more thing before you call me on it -- i understand fully that factory ecm/pcm's are not designed to operate two sets of injectors. however, i'm fairly certain that with a combination of wiring the appropriate injectors in series (i.e. cylinder 1 primary and cylinder 2 primary) and modification to the parameters of the ecm/pcm that i can use an oem ecm/pcm to batch two sets of injectors properly. as far as details on concerned -- it would require more research on my part -- however again this post was simply to gather general info on oem vs. aftermarket computers.

[This message has been edited by ImportEater (edited November 07, 2001).]

Well, I have 55s in my little 231 V6 and it idles just fine (700 rpm in gear).
The 1228331 vette ecm fired 2 sets of 8 injectors (ZR1 Vette).

No aftermarket company has invested anything like GM for ecm design. Just about bullet proof. For $40 you can carry a spare. The oems generally start talking to you at $400 for any repairs, and then want to update you to the newer models that they just happen to sell.

When you sand bag your guestions, it makes it hard to guess about what you're wanting to do.

How about a list of what your wanting to do?.

You started with a simple open ended question, then mentioned turbos, now DIS.

Then you qualify things with 60s not being able to idle decently, when in fact they will.

the aftermarkets are meant to be easy to program, and simple to learn. They also can support Peak+Hold injectors. If you want the best in ignition systems then you'd want an eDIST