efi-diy

Please excuse the cross post....

https://www.thirdgen.org/forums/dfi-...7-harness.html

This may be of interest to folks running TBI especially with higher HP engines.... by running MS you can fire both injectors at the same time effectively doubling the fuel flow. With 90# injectors this means a 360 to 380 HP motor is supportable.

http://profile.imageshack.us/user/ef...7100026li5.jpg

Fast355

iTrader: (2)

Just because you are firing the injectors 2x as often, doesn't mean that you are accomplishing anything. The TBI injectors already have 1/2 the time to fire that normal MPFI injectors do. I like to fire the injectors in ASYNCH at higher RPMs anyway, that gives them more total open time.

I can support 400+ HP with 61# injectors, just not at the stock fuel pressure. I run 40-45 PSI.

The TBI PCM is a MUCH better solution for most TBI users.

efi-diy

Sorry but I disagree with you ... GM programed the TBI injectors to fire Async except on start up where both injectors fire in Sync. So by firing the injectors in sync all the time for the same amount of time as you do ASYNC then the fuel flow is doubled.
I recently tuned a hot 355 that was running way lean with a custom Jet chip. During the initial tuning run the owner commented that this was the first time he had seen the truck run rich since putting the new engine in.

As far as "The TBI PCM is a MUCH better solution for most TBI users."

This depends on your skill set and having the equipment to burn eproms - I did it for a while and got fed up.
I agree its not for everone as its much more DIY, you can't get on the phone and say I have XYZ cam, heads etc and then a chip shows up that maybe be OK but its a shot in the dark.

Also, no you can't go down to your corner auto parts store and get a replacement box.

But once you get the first 10 min's of tuning time done and find out how easy it is - you quckly forget about burning eproms, a few taps on the keyboard the the mixture/timing dials in much faster. If the target vehicle has a wideband 02 installed then you just drive it, datalog and then run the optimization program and within 30 min's you have a good baseline tune up thats drivable. If your a commercial tuner, this cuts your tuning time in 1/2 so you can do 2x the amount of vehicles in the same amount of time.

Cost wise a custom chip from Jet is about $500 - a MS setup is about $400 plus the cost of a used laptop.

Fast355

iTrader: (2)

The TBI PCM is VERY easy to tune compared to the earlier setups, I have even been running a MAF on mine. MAF is MUCH easier to tune than SD ever thought about being with a TBI setup.

Hate to break it to you, but you will NOT GET 2x the fuel, it is NOT HAPPENING. Its a little thing called duty cycle. When you hit 90ish % duty cycle, the injectors start going STATIC. That means they hit their rated flow numbers and offer no more fuel. I don't care if you are firing them once per crank rotation or 10 times per rotation. The more times they have to open and close per crank rotation, the less fuel that is injected. Injectors take time to open and close. At 6,000 rpm, a TBI injector that is operated in SYNCH with the engine is opening and closing 200x a second. In asynch they are only opening 80x a second. See a dramatic difference. It can amount to a 20% or more difference in fueling.

BTW- Later model TBI trucks ran in ASYNCH under heavy loading.

The TBI PCM setup is cheaper than that.

$50.00 PCM with Memcal
$85.00 Burner
$55.00 Adapter and Chip package
$10.00 worth of ECM harness pigtails from wrecking yard
$30.00 knock sensor

I get $230+ used laptop

You can add a 85mm GM MAF for another $100.

For $350.00 you can be up and running on a completely tune-able setup, running the BEST GM TBI computer, AND run MAF.

If I was spending money to buy a tune-able ECM setup, it would be the Flash EBL.

EDIT- I am running a TBI PCM run TPI setup using an 85mm MAF for fueling control.

efi-diy

Agreed that the later model flash based ECMs are easier - this is meant to help tune the eariler '747 type installations. And if you so desire you can program the injectors to fire ASYNC in MS so you have it either way.

Fast355

iTrader: (2)

I have messed with mega-squirt and I am sorry to say, the stock GM stuff is still better. Get into the source code side of it and you will see why. The stock stuff tends to be much more adaptable, which leads to improved operation over a wide range of operating conditions.

My TBI 350 was making nearly 500 HP at the Flywheel. Putting down over 390 RWHP through a 700r4 and a GM Corporate 14 bolt rear-end. Using a STOCK GM TBI PCM, with a re-written code.

efi-diy

Ah there is the key "re-written code" - glad to see that you can program in MOT assembler and/or C. Just not many folks have that skill set.
I never said there was anything wrong with the GM electronc's is not as easy to tune as a flash based retime programable system.
This is an alternative.

Not sure when the last time you tried MS - if it was MS1 - then yes I agree with you while it worked it did have limitations. The newer MS2 code is greatly improved. And yes if you so choose to, you can re-write the MS embeded code as its open source, and I'm sure the the MS folks would welcome your help.

Fast355

iTrader: (2)

The extent of the code rewriting was to get a higher rev-limit, as well as fueling, timing, and shift control for over 6,400 rpm. Not something that a normal TBI user would need. I have also written a little code for a 2.2 S10 Flex Fuel sender and Dual Speed fan control for the LS1 cooling fans. I am currently working on DIS for the same ECM, it was used with this ECM in 2.2 S10 powered trucks.

It was MS2, FWIW.

efi-diy

The fuel delivery points above are being discussed off line to come to a mutual understanding... we're both right under certain conditions.

RBob

iTrader: (1)

You really don't know what you are talking about, do you? Please explain what async & sync injector firing is in a GM TBI ECM.

RBob.

efi-diy

Actually I do know what I'm talking about and I am preparing a proper technical answer to ensure that this question is put to rest.

From what I can see is that your upset since this is direct competition to your products.

efi-diy

Actually I do know what I'm talking about and I am preparing a proper technical answer to ensure that this question is put to rest.

From what I can see is that your upset since this is direct competition to your products.

Fast355

iTrader: (2)

Actually, I don't think that RBob is upset with anyone, much less feel that he is threatened by Direct competition. MANY people making power in the TBI world are using his EBL and even updating to his FLASH EBL.

The EBL is a complete Tuning System that is oriented toward TBI and offers MANY refinements above the GM ECM, which as you know I already feel is better than MegaSquirt or even MegaSquirtII.

RBob

iTrader: (1)

Well, it has been 2 days since my post. So either you are still researching what sync & async injector firing on a GM TBI ECM is, or you have completed your research and have concluded that you do not know what you are talking about.

As for direct competition to my products, sorry, not even close competition. How do you compare an experimental unit (directly from the MS web site) to a fully engineered system (the EBL). You can't.

RBob.

Street Lethal

iTrader: (16)

EBL > MSI/II =

efi-diy

?

Street Lethal

iTrader: (16)

^ "Well, it has been 2 days since my post. So either you are still researching what sync & async injector firing on a GM TBI ECM is, or you have completed your research and have concluded that you do not know what you are talking about"....

Well...?

efi-diy

Re: GM '746 & '747 harness to megasquirt adapters
Quote:
Originally Posted by RBob
Well, it has been 2 days since my post. So either you are still researching what sync & async injector firing on a GM TBI ECM is, or you have completed your research and have concluded that you do not know what you are talking about.

As for direct competition to my products, sorry, not even close competition. How do you compare an experimental unit (directly from the MS web site) to a fully engineered system (the EBL). You can't.

RBob.

Actually I do know what I'm talking about, with GM '747 the max time available in ASYNC mode to inject fuel in 4.5ms at 90% DC. This is due to the fact that GM fires either inj. A or B every tach pulse - when the DC exceeds 50% it skips the tach pulse. So both injectors are firing at the same time.
Here is the kicker with MS you can fire them in SYNC (for a V8) 1,2,4, or 8 times (8 times is what GM uses) every engine cycle, by skipping tach pulses e.g. firing twice per engine cycle you gain injector opening time thus allowing more fuel in.

MS outsells the nearest retro-fit EFI unit by over 2:1.

My aim here is not to **** on other people or their products its poor form... But to offer an proven alternative to burning eproms.

The fact that you offer a flash based tuning product - good for you. Its still restricted to the GM hardware that is over 10 years old and that won't change.

Folks can decide for themselves where the truth lies here.

BMmonteSS

What he's saying is that even the megasquirt II can't hold a candle to the EBL system.

Street Lethal

iTrader: (16)

Could have fooled me lol. A lot of the member's here are very familiar with the MegaSquirt system, it's nothing new. I've personally known three members here that went with this setup, and two out of the three went right back to the stock GM ECM (albeit, enhanced). Interesting thing to note; all three members had to solder the internals of they're units upon arrival, which doesn't say too much for the source behind such a "wonderful" product....;



Incidently, before you continue on with this argument that is clearly going absolutely nowhere on your part, know that you are arguing with a moderator who has an impeccable history here with us, and has been a tremendous support, and backs his product one hundred percent. Unlike MegaSquirt's "forum" of information, where facts seem to vary, Bob personally answers each and every question presented, himself....

Fast355

iTrader: (2)

You should also mention that he has been playing with the 7747 almost since GM started building them.

I haven't exactly been sleeping with my back to the TBI world either.

I have played with 4 different ECM solutions for TBI setups. Stock GM ECM, EBL, MegaSquirtI/II, TBI PCM (MAF too).

The original poster is off with his Async description.

Asynch is simply a mode that fires both of the injectors at a fixed 80hz. That is once every 12.5 MSEC, regardless of engine RPM. Synch mode fires the injectors in an alternating pattern every other distributer reference pulse.

efi-diy

1) assembled MS units are available in surface mount if so desired. The standard kits need to be assembled.
2) I agree that this thread is going nowhere positive.
3) The adapter board is available and I'll let folks decide if they wish to use it.

efi-diy

OK fine - thanks for the correction - now everone is clear on this.

alvanwie

efi-diy,

If you came on here to push your adaptor board I don't think anyone would have had a major problem with that, since yes it may have helped someone who wanted to change to megasquirt.

But you did NOT have your facts correct, showed too much attitude, and took a cheap shot at probably the most knowledgable and helpful member on this board. This is not the way to make yourself know here.

And yes I do run a 400 hp tbi engine with the 746 ecm thanks to a lot of help from Rbob (even though I do no run EBL) and many others on this board.

AL

efi-diy

Your correct.. To all if I have upset anyone - I applogise.

I based my orginal facts on measurements for a half working ECM - that I found out when I went to repeat the measurements over the weekend - it wouldn't go above 50% DC.

EFI-DIY

RBob

iTrader: (1)

This is incorrect. First lets define sync and async injector firing. Async injector firing is both injectors every 12.5 msec (80 times a second). Or asynchronously to the spark plug firings. And, they fire together, both injectors at the same time.

Sync injector firing is when the injector firing is synchronized to the spark plug firings. In the case of GM TBI ECMs they are set up to fire the injectors alternately on each plug firing.

The ECM TBI ECMS do not skip injector firings in sync mode. The item you may have missed is that the injector firings will overlap. When you see the injector duty cycle over 50% they will be overlapping, the current open injector will stay open as the other injector is commanded to open.

At 100 %DC, both injectors are open all of the time. When this point is reached more injector flow is required.

This may sound like a nifty feature, but skipping injector firings results in poor fuel distribution. There will be cylinders that inhale air, but little fuel. Then once the injector fires, the currently inhaling cylinder will get a lot of fuel. Half or more of which is supposed to be for other cylinders.

Doesn't make it better then the others.

There are other alternatives that have been around for years: Prominator, Ostrich, Romulator, AutoProm, the SRAM MEMCAL (can't recall the name), etc.

The hardware isn't the end all to be all. The software/firmware is more important.

RBob.

efi-diy

Here is the kicker with MS you can fire them in SYNC (for a V8) 1,2,4, or 8 times (8 times is what GM uses) every engine cycle, by skipping tach pulses e.g. firing twice per engine cycle you gain injector opening time thus allowing more fuel in. This may sound like a nifty feature, but skipping injector firings results in poor fuel distribution. There will be cylinders that inhale air, but little fuel. Then once the injector fires, the currently inhaling cylinder will get a lot of fuel. Half or more of which is supposed to be for other cylinders.


I have run in my own vehicle in this mode and the engine does not complain e.g. runs identical to triggering on each tach pulse. Now if you set to injector once per engine cycle - yes it does make a difference - fine at wot - not so fine at part throttle.