ACCELL GEN 8 vs BS3

[Rybar]

Hey guys, have a close friend who is having a shop build him a new motor and was wondering which system would be better suited for his setup:



Here are a few specs, sorry I don't know the full details:

4th gen 1994 Trans Am - T56 6-speed
Strange 12-bolt rear 3.73
420 cu in Iron block LQ9 - Gen III
8.6:1 compression
D1SC Procharger Intercooled
Dart 225 heads ported
cam specs ???
Edelbrock 1/7/8 LT headers
Custom dual 3" exhaust

He is also wondering what RWHP and Track times to expect from this car. I think the car is around 3600 #

[INTMD8]

No reason to run either.

The stock PCM with HP Tuners 3bar Speed Density operating system would be the best option for that combination.

[camcojb]

No reason to run either.

The stock PCM with HP Tuners 3bar Speed Density operating system would be the best option for that combination.

well hell, I'll throw my BS3 away tomorrow................... First off, he never said how much boost he was going to run, so 3 bar is presumptive. Also, besides the extra features like nitrous and boost controls that the BS3 and similar have, they have a huge advantage over the stock computer on forced induction.................... a true wideband and closed loop wide open throttle controls.

With all that said, the stock ecu is very good and I've used both HP Tuners and EFI Live with great success, just wouldn't have made such a blanket statement.................

Jody

[INTMD8]

He said D1SC on a 420ci engine. I think it's safe to assume that combination won't be eclipsing 30lbs of boost so a 3bar sensor should be adequate, as should the stock ECU.

I never use the built in BS3 boost control. I like on the fly adjustability.

He posted his combination which is what lead me to my recommendation so I wouldn't really classify it as a blanket statement.

Just as if he said "427ci LSX 6-bolts/cyl 11-1 comp, solid roller, twin 76's" I would have recommended the BS3

[camcojb]

He said D1SC on a 420ci engine. I think it's safe to assume that combination won't be eclipsing 30lbs of boost so a 3bar sensor should be adequate, as should the stock ECU.

I never use the built in BS3 boost control. I like on the fly adjustability.

He posted his combination which is what lead me to my recommendation so I wouldn't really classify it as a blanket statement.

Just as if he said "427ci LSX 6-bolts/cyl 11-1 comp, solid roller, twin 76's" I would have recommended the BS3

but how do you know he's running over 15 psi? No reason to give up the resolution using a 3 bar when a 2 bar is fine.

I don't use their boost control either, just listing it. The wide open closed loop is a definite advantage in my opinion.

Jody

[INTMD8]

Jody,

Even with the 3 bar sensor on the stock ecu the VE table has about double the resolution of the BS3 w/3bar. 2bar has even more resolution yes, but it is allready excellent with 3bar and perfect driveability is easily achieved.

If I'm tuning a forced induction combination it is with the 3bar sensor so the car doesn't have to be extensively re-tuned when upgrades are made in the future.

Even with the BS3 system I turn off wide open closed loop as it slows the car down. Running straight off of the VE table when the ecu is making zero corrections makes the car the quickest/fastest/most consistent in my experience. Even on a tune with just 1% correction running the car in open loop can increase trap speed 1-2mph on an 8sec car.

-Jim

[camcojb]

Jody,

Even with the 3 bar sensor on the stock ecu the VE table has about double the resolution of the BS3 w/3bar. 2bar has even more resolution yes, but it is allready excellent with 3bar and perfect driveability is easily achieved.

If I'm tuning a forced induction combination it is with the 3bar sensor so the car doesn't have to be extensively re-tuned when upgrades are made in the future.

Even with the BS3 system I turn off wide open closed loop as it slows the car down. Running straight off of the VE table when the ecu is making zero corrections makes the car the quickest/fastest/most consistent in my experience. Even on a tune with just 1% correction running the car in open loop can increase trap speed 1-2mph on an 8sec car.

-Jim

I'm speaking of street cars and safety. If that tune is off, if the weather changes I still like wot closed loop. I have never done a max effort deal, so you're probably right. I've made over 1000 hp on 91 octane, and that's about where I am now with my Chevelle; never gone beyond that. The guys on here are usually driving them on the street.

Again, I love the factory computer, but I do know things change with it. I had a twin turbo on an 05 GTO with a maf and factory computer. Hated tuning with pe since the maf was maxed. They didn't have speed density yet. I did notice depending on the weather my wot a/f would change. Speed density may have been different, don't know.

Thanks for the info, you've apparently been around the block before, appreciate it.

Jody

[INTMD8]

Jody,

Yes a MAF/forced induction car tuned with the PE table will definitely change with the weather. If you're tuning with a maxed maf and outside air density increases you will have no added fuel at that point. That is why I dislike that setup.

The speed density setups when tuned correctly seem to work very will in different weather and altitude. I tuned a car here in schaumburg (just north of chicago) that went to Denver and was re-tested on the dyno and the tune was still right on. (fwiw I am the tuner/fabricator at www.speedinc.com )

My own car running 2.5bar speed density on the E38 ecu has also been very consistent as I've logged it on the street and track with the dynojet wideband in various conditions.

I'm not saying that closed loop wideband at WOT is a bad thing but I don't think it's absolutely necessary either. For instance with the dynojet wideband you can program it to trigger a warning light if the car is running too lean past a certain rpm/tps point.

-Jim

[camcojb]

Jody,

Yes a MAF/forced induction car tuned with the PE table will definitely change with the weather. If you're tuning with a maxed maf and outside air density increases you will have no added fuel at that point. That is why I dislike that setup.

The speed density setups when tuned correctly seem to work very will in different weather and altitude. I tuned a car here in schaumburg (just north of chicago) that went to Denver and was re-tested on the dyno and the tune was still right on. (fwiw I am the tuner/fabricator at www.speedinc.com )

My own car running 2.5bar speed density on the E38 ecu has also been very consistent as I've logged it on the street and track with the dynojet wideband in various conditions.

I'm not saying that closed loop wideband at WOT is a bad thing but I don't think it's absolutely necessary either. For instance with the dynojet wideband you can program it to trigger a warning light if the car is running too lean past a certain rpm/tps point.

-Jim

thanks Jim. I'm just an enthusiast who likes to do his own tuning and building hot rods. That whole LS2 speed density deal was a bummer. Keith (HP Tuners) could give me no idea when 2 bar speed density was coming out, so I gave up on the maxed maf/PE deal and sold the twin turbo kit and the 05 GTO. Two weeks later they had the tuning, I was not a happy guy. I loved that car other than the tuning limitations at the time. I would still own it if he'd given me a bit more info; he told me it could be another year before it was available, and then came out with it less than a month later.....................

Jody

[INTMD8]

Yeah that sucks, I know many people were waiting a long time for the speed density operating system. Not sure what the hold-up was but I'm glad I get to use the finished product rather than design it

[gkring]

I always recommend use whatever the guy tuning it wants you to use. If you are going to do it all yourself and have no prior experience I would go with the big Stuff or a FAST system since it is easier to find help and support over the Accel DFI. I have not heard of Gen 8 yet so I would imagine support for it to be even worse than the Gen 7. The motor he is building I would not recommend someone try to tune without help.

[Rybar]

Thanks you guys, I beleive he is going with the latest Accell system since that is what the builder recommended. For boost I also beleive it will run around 15 #'s give or take a bit. I highly doubt it would see 30 # as it will be a street car that he will take to the local 1/4 mile track once in a while.

[Blown353]

Hey Jim, maybe you can answer this, because I've never got a satisfactory answer elsewhere (including the EFI Live & HP Tuners support forums) and you appear to have the experience:

How does a factory ECU handle barometric pressure changes with a speed/density operating system in a forced induction vehicle? There is no longer a MAF sensor which can easily determine realtime air density, and the ECU can't take WOT MAP reading to update the baro parameter in a forced induction combination (and that's not the best way anyways, even naturally aspirated.) As far as I know, there is no 2nd real time atmospheric MAP for real time barometric updates with a factory ECU.

BS3, Pantera, and Megasquirt for example all have the option of second MAP sensors for realtime barometric updates.

This is very important for me as I can drive from sea level to 9000' in 2 hours on the same tank of fuel without ever shutting the car off, so I need a way to update the barometric pressure without a key off/key on refresh of the barometric pressure at startup.

I initially threw out the option of using a factory E38 ECU in speed/density with my new twin turbo LS2 simply because nobody can give me a satisfactory answer how a dramatic altitude change in a forced induction is handled without the MAF sensor other than a key off/key on cycle... but I'm all ears!

[MonzaRacer]

OK for the record what you need is the max psi rating for the forced induction. This needs to be reduced to a BAR reading 1 bar, 2 bar, 3 bar, 4 bar. The bar rating is how high of boost or positive pressure it can read.
A 2 baro system may be used for a simple at rest/startup reading and then another for running reading.
But all the GM stuff uses a 2 or 3 bar barros sensor if no maf is used.
You dont need a second baro sensor just properly rated one. Then the ECM simply uses properly programed V/E tables related to the baro sensor reading.
As for the best way to go I prefer the cheaper system Megasquirt. And its adaptable to just about anything.

[Blown353]

OK for the record what you need is the max psi rating for the forced induction. This needs to be reduced to a BAR reading 1 bar, 2 bar, 3 bar, 4 bar. The bar rating is how high of boost or positive pressure it can read.
A 2 baro system may be used for a simple at rest/startup reading and then another for running reading.
But all the GM stuff uses a 2 or 3 bar barros sensor if no maf is used.
You dont need a second baro sensor just properly rated one. Then the ECM simply uses properly programed V/E tables related to the baro sensor reading.
As for the best way to go I prefer the cheaper system Megasquirt. And its adaptable to just about anything.

FYI... Megasquirt-II now uses 2 separate MAP sensors-- one for manifold pressure and one open to the atmosphere to read barometric pressure to take care of barometric (altitude/weather) changes in real time. The MS-II can also do barometric updates at key-on if you only use a single (manifold) pressure sensor, but if you experience a big change in altitude it can shift your VE & tune and you'll have to key off/key on to reset the barometric pressure stored in the ECU.

I just want an answer of how for example a factory GM E38 ECU with an aftermarket Speed Density operating system like HP Tuners or EFI Live compensates for realtime barometric pressure changes in a forced induction vehicle without a key on/key off cycle as there is no MAF to determine real time air density, and there is no 2nd MAP sensor for realtime barometric pressure updates. With only a single MAP sensor, that leaves the only realtime barometric update scheme to be a baro refresh at WOT, where manifold pressure should be pretty close to ambient barometric conditions-- but in a forced induction engine that is not a valid approach. Thus you're left with relying on a key on MAP value as the barometric pressure, but then if you drive over a dramatic altitude change it would require a key cycle to update.

[Fuelie Fan]

It would rely on its learned fuel trims during a single trip as you described

[INTMD8]

blown353- you are correct, without a key off/key on cycle baro will not update as it would not be possible with one map sensor and forced induction. As mentioned, you would have stft and ltft's which are applied to wot but I have no real experience logging a car that has driven from sea level to 9k feet in a matter of hours.

[Blown353]

blown353- you are correct, without a key off/key on cycle baro will not update as it would not be possible with one map sensor and forced induction. As mentioned, you would have stft and ltft's which are applied to wot but I have no real experience logging a car that has driven from sea level to 9k feet in a matter of hours.

Thanks for the answer, you confirmed my assumption about needing a key cycle. I really wanted to try a factory ECU for my new twin turbo LS2 build but the lack of realtime barometric comp when in speed density nixed the idea for me-- sometimes on weekends I go on "fun runs" up to the mountains and with my current oldschool FAST I would have to reload a new tune for the high altitude stuff... that was a pain in the butt.

[Fuelie Fan]

I would be curious to know if the ZR1 has an additional baro sensor. Or what about all the turbo ecotecs and supercharged 3.8s?

[COPO-RAT]

Sorry to hijack the thread with such an ignorant question, but can someone shed some light on exactly what a GM E38 ECU is and where they are used? It's a factory ECU that's capable of running a high performance fuel injected motor?