DanS

iTrader: (1)

I have a 305 TBI car that plan on building a 383 for. The goal is to have a very streetable n/a 11 second car. I was going to convert to TPI, but the high-flow parts are so friggin expensive.

So, now I'm looking into the Holley Commander 950 4bbl TBI set-up. Does anyone have experience with this? What would be some disadvantages of using it (besides emissions)? Which route would you guys go?

Dewey316

i would either go with something like the stealth ram, or mini-ram.

or a big 900cfm tbi unit, like you are looking at, or a carbed manifold drilled for injector bosses, and a 1000cfm TB on top of it.

then of cousre, big cam, and big heads

really any of them should be able to get close to 11's, i hear the 900cfm holley units are only good for about 500hp, so if you goal is more than 500, you might look at the MPFI systems with a big carb manifold, or HSR, or mini-ram.

FASTRED335

On a budget which most of us are, I personally like the 21S-4bbl TBI rated at 575 max hp for the 383, it cost considerably less than MPI or RAM injection, and is not that far behind in horsepower plus you can always squeze more hp out of them. (TBI)

kdrolt

See:

https://www.thirdgen.org/techbb2/sho...hlight=900+cfm

Paraphrasing Rbob from the cited post:
They used three different induction systems, all run by the Holley 950 Commander ECU, and all tested on the same long block engine.

Both port systems used 30# injectors. First up was the MPFI (multiport FI) system. It is a single plane carb-style manifold with a 1000 CFM carb-style throttle body (system #91004101).

Second, the TBI system is a Holley 4 bore TBI 700 cfm unit (# 950-22S) that was placed onto the MPFI manifold (with the port FI disabled, and instead using the TB injectors).

Third, the StealthRam manifold, which was fitted with a 58mm throttle body (rated around 1050 cfm). And of course it has the short runners and huge plenum.

The StealthRam had the most output, peaking at 405HP/425FT-LB while the TBI peaked at the least among the three units tested (395HP/414FT-LB). The MPFI system (port injection, 4 bore throttle body) was generally in between these two.

The comparison test is useful for 4bb TBI to TPI because the stock TPI has been shown to be a lot less powerful than the StealthRam, and even a highly modified TPI is still not as strong as the StealthRam. So the fact that the 4bore TBI was only down by 10 hp and 11 ftlbs shows that TBI isn't quite as bad as others might suggest.

Note further that the TBI was tested with a 700 cfm throttle body, while the other two systems used 1000 cfm throttle bodies, so we don't really know what the TBI would have made for power had it been equipped with Holley's larger 900 cfm TB. But Holley might....

Lastly, the above specifically refers to testing a 4 bore TBI unit, not the factory 2 bore units made by Rochester Products of GM. Those units are limited to around 550 and 670 cfm flow respectively for the small and large TBs, so the best power output using them can be expected to be less by a factor of airflow ratios.

Go read the original thread, and get a copy of the magazine story for more details. HTH.

DanS

iTrader: (1)

Thanks for the insight, guys. :hail: The Holley 21S-4bbl tbi is looking better & better. What does it take to get the stock gauges & cruise to work with this system? I've searched & all I kind find are posts stating that it could be done, but not much info on how.

dennis6

HSR is 299 for the manifold and plenum. -summit
Fuel rails are 175.95 for fixed pressure and 219.95 for adjustable -summit
Injectors $50 dollars off ebay
TPI computer 20 bucks off ebay
TPI harness 100 dollars off ebay
Various sensors about 100 dollars
TB is about 50 dollars on ebay
HSR setup can be had under 800 dollars. What is so appealing about a TBI setup?

25THRSS

Are you comparing used HSR parts to new tbi stuff???? That is just plain stupid. If you wanna compare things do it right. Like the above post stated, the tbi setup, with everything else being equal is right with the stealth ram, if not better, and when you compare things FAIRLY, the tbi will be cheaper. A lot of guys who already use 4 barrel manifolds can save some money by sticking with what they already have as well. Don't be a ***** and try to compare ebay parts to new tbi parts.

nick harmon

hey man theres no question,tbi all the way:rockon:

dennis6

I was showing how to do a MPFI swap cheaply, rude remarks not appreciated. The actual HSR parts were new. The supporting parts were used.

TBI is nothing more than a carb with injectors. A 4bbl TBI is a modified carb with 4 injectors. It can not compare with the tuneablitly of a MPFI injection system. If you want something cheap and simple, go with a carb like I did. If you want a infinitely tunable setup that gets good gas mileage go for MPFI. TBI is great for a daily driver where power isn't a factor, but why did you buy a fbody then?

That being said, magazine comparisions are for entertainment purposes only. The comparision is not valid, because it doesn't show the amount of torque produced or what the hp and tq numbers were throughout the curve. Peak HP is only for the import crowd.

Holley gave them those parts for free, so they are going to produce a setup that makes both of them look good.
They could have spent 1 week tuning the TBI and 1 day tuning the Stealth Ram. There isn't enough data to come to the conclusion that TBI will run with MPFI.

dennis6

Kinda funny that a TBI setup has a problem after 500hp, if they are equal to a MPFI system or better.

Dewey316

#1
the commander 950 tbi based, or MPFI base, ahs WAY more tunability than any of the TPI computers. it also also alows for real time changes. something that TPI does not.

#2
as for the HP and TQ curves, that has way more to do with the intake manifold, heads and cam, then it does with how the fuel gets there. the runner lenght, plenum volume, cam duration, ect detirmine that, all that MPFI is vs TBI is how the fuel and air mix. the engine doesn't really care how the fuel and air is mixed, all that determines power, is how much fuel/air make it into the cyl on the intake stroke.

#3
also not those power level were comparing a 700cfm wet flow system vs a 1050cfm dryflow. there is a BIG diffrence there. if the stealth ram was really the hot ticket here, it should have blown away the TBI system. especialy considering the HSR plenum size, i bet it is much larger than the signel plane they were using. put a single plane with a similar plenum size to teh HSR, and i bet the TBI does even better.

dennis6

Using new parts all from summit.

HLY-7540 Stealth Ram TPI Manifold, SBC 1957-86, Idle To 6000RPM, Satin $299.95

HLY-534-185 Fuel Rail Kit, HLY-7540 Stealth Ram, w/ Non-Adjustable Regulator $175.95

ACC-150824 High impedance, 24 lb./hr., replacement,
performance fuel injector set $229.95

BBK-1537 Chevy/Pontiac: 1989-92 305,350, twin 52 mm, throttle body $299.95

PRF-60103 GM: 1990-92 5.0L, 5.7L, TPI wiring harness $296.95

Sensors 100 dollars from autozone.

This is for a Speed Density setup, and the only used part I advocate using is ECM, a holley unit is not requried in this case. The ecm can be had for 20 dollars. Fuel pump should be swapped either way so its not an issue. 383 uses a little more fuel than a 305, and a 4bbl uses more fuel than a 2bbl.

We don't know if they guy posting this has a carb intake manifold, so the HSR may actually be cheaper. If he has to buy a laptop, interface cable, and carb intake, the HSR will be cheaper.

Dewey316

that is limited by the injector size, and air flow of the TBI, the largest you can get is a 900cfm. if you could get a 2000cfm unit 120lb/hr injectors, you wouldn't have that 500hp limit.

dennis6

#1
People on the DIY prom board would beg to differ.

#2
Try throwing a wild cam into your TBI engine and see how easy it is to tune for.

#3
Need more testing than one magazine article to establish TBI as a viable contender to MPFI.

dennis6

The only time I see TBI as better than MPFI is in dual quad setup. Then you would have the same number of injectors plus a more even air distribution.

Dewey316

#1
how many people are that computer savy to do code patches, ect.

#2
we aren't talking about the 160baud 746 ecm here, we are talking about the commander 950 ecu, which would be much easy to work with, just because of the ability to gather the data it has.

BTW, my cam specs.... 210/218 .525 .525 112 in a 305.

#3
yes i know this, but we also need more than you opinion to dismiss it.

dennis6

This isn't gonna get us anywhere, and I don't have the money to prove/disprove my opinion and thats all anyone here can have untill more testing is done. So I am agreeing to disagree and leaving it at that. As I said earlier I went carb, as fuel injection doesn't fulfill my priorites, a decent balance of price and performance, I think that has alot to do with my view point.

BTW my TBI setup is for sell in the classifieds section.

nick harmon

is probably the best thing givin data and current tech. but theoreticly two fuel injection systems one wet manifold and one dry manifold both with perfectly matched cfm capability, the wet manifold would be just as powerful at idle and just off idle-and definitly more powerful at really high rpm ranges, and for sure more consistent than the dry manifold. we all know that engines do not like hot air, right or wrong? :lala:

nick harmon

im sure some gearhead with a few engineering degrees is working on it now.

dennis6

Ofcourse engines don't like hot air, but I don't know how much cooler if any the air coming into the engine from a TBI setup is. I would say probably none. Think about it, the coolant temp sensor is in the intake manifold. They both run the same temp.

nick harmon

okay, im no rocket scientist, and certinly dont grasp the theory of
thermodynamics, but run a tpi car and a tbi car 5 times down the track and tell me which manifold is hottest. you will never see me at the track with ice packs on my manifold between runs.

Dewey316

why would one be cooler than that other?

if you are getting at the fuel charge dropping the air temp, then i would think TPI would actualy have the advantage, since it introduces the fuel charge later , so the actualy a/f charge going into the cyl. would be cooler than one that has traveled through the intake plenum and runners first. TPI would also have the advantage of having a gap between the manifold and plenum, which would again, help keep the air charge cooler.

nick harmon

good point, but then why do tpi guys have to cool their hiperformance manifolds? not arguing, just asking.

Dewey316

the same reason people have cooled their manifolds for years, be-it carbed, tuned port, TBI, or whatever. when you are racing for every thousands of a second, every little bit helps.

nick harmon

why do people say its so hard to get tpi to flow well past 5000rpm without an almost total rebuild with expensive aftermarket parts?

Dewey316

because of the long runner design. it doesn't not lend itself to high reving power.

nick harmon

then why does every one sh#t on tbi, and worship tpi?

Dewey316

beacause TBI got the crappiest heads GM ever made, they got a joke of a cam, and in stock form flows almost no air.

nick harmon

but it seems relativly easy to fix all that though with the right amount of elbo grease. to be honest i just want to dust tpis and mustangs with so called lowly tbi.

Dewey316

ok, so do you have a question? we all want to dust everything

nick harmon

alright, alright point taken.

dennis6

All of TPI's problems are cured with a HSR or LT1 intake, both are about a 500 dollar change. Port the heads and change the cam, and I don't see how a 2 barrel TBI could ever compete even with a head and cam change.

Dewey316

run the same cam, and same heads, on a HSR, with the stock TB, compare it to a 4bbl intake w/ high-flow TBI, and see what how it compares the HP is always going to be limited by the limiting factor in an engine. with the HSR in an aftermarket head/cam engine, the limiting factor is going to the TB, if you spend the money for an aftermarket throttle body, and HSR, you could buy a 900cfm TBI system, which would be good to about 500hp, not many people are going to build a NA small block, at least in a street driving computer controled car, that is much above 500hp. granted a 670cfm limit, is going to eventualy get the TBI, but that would be above the 300hp mark. ALL things being equal, i still have yet to see anyone have a good reason why TPI is any better.

DanS

iTrader: (1)

Wow, looks like I've stirred up quite a debate. This wasn't my intention, but it's definitely makes for interesting reading.

The HSR looks good, but the cost of new parts that dennis6 listed comes around $1,400. Add in a fuel pump and chip burning equipment/software, and the total comes closer to $1,900.

Here's why I like the idea of the Holley 21S set up. It's $1,400 new, just add a carb intake for <$200 and you've got a set up that will handle 450-575hp (according to Holley). It comes will a fuel pump & all sensors.

Yeah, the $300 total difference isn't really that much when spending that kind of money, if the HSR would give better results. But, I'm not sure it would. As a novice tuner, it seems that I would probably end up with much better tuning using the Commander 950, than trying to figure out the GM ECM (without spending a year learning it). It seems that a properly tuned TBI is going to be more efficient than a poorly tuned TPI set up. Plus, when picking out the heads & cam, there is much more dyno info available on carb intakes than the HSR (not sure how the HSR is going to change the power curve).

I could be way off on all of this, but that's why I'm looking for advice.

Dewey316

i like the way you put that!!!

i am still not convinced you will see any power gain from the HSR over a 4bbl.

also does anyone know what gasket the HSR is cast too? i know you can get 4bbls that are cast to HUGE gaskets sizes 1206 ect. and then if you get heads with an equaly large port, you can flow some serious air.

nick harmon

okay, could some one please tell the dumbass (me) what the f*@k an HSR is?

DanS

iTrader: (1)

Holley Stealth Ram
It's a high-flow TPI intake.

nick harmon

thank you. as you can see i have little to no interrest in tpi products because even if i made 35000$ a year (probably chump change to alot of our members) i still couldnt afford that stuff.
thats why i have to stay with tbi. its also my first step into fuel injection. now i can build some low tech carbed monsters, but some day i know i will have to have fuel injection on my carbed dodge too. which is why i joined you hi-tech gearheads!:hail:

dennis6

Holley Steatlh Ram is only 500 dollars for plenum and base.
Fuel rails are around 200 dollars.
The rest you can get off ebay or Hawks for about 400 dollars.

I know some of it is used, but you don't need all new stuff...

Or you can pay $1300 for a new Holley 4 barrel TBI setup, your choice.

Dewey316

of course you forgot to add the $500 for the new hood that the firebird owners need....

dennis6

http://www.stealthram.com/ Good comparison of intake systems and HSR ability.

As for the hood issue that would be a factor in not getting a HSR. However, you could always get a BBK 1000 cfm throtle body that fits on a carb intake, a victor EFI intake, Edelbrock fuel rails (cheap!!!),Accel injectors, and a Holley 950. No hood clearance issues this way. Probably could run it off a TPI computer somehow.

dennis6

The advantage that MPFI has over TBI is 8 injectors versus 2 or 4max. This allows for better fuel distribution

DanS

iTrader: (1)

Just an update for anyone who is interested, or who stumbles across this while researching their own projects.

After a ton of research and changing my mind back and forth, I've decided to go with the stealth ram, and a tpi ecm. My main reasons for looking into the commander 950 4bbl set-up were cost & ease of tuning. After reading Holley's tuning manual for the Commander 950, I realized that tuning it is essentialy the same as burning proms (only with a nicer interface). Overall cost for the stealth ram is a little higher, but I think it will be worth it to have port injection. Also, I couldn't find a good way to keep my electronic speedometer, with the 950.


Thanks for everyone's input. Now's it's just a matter of saving for the parts.

r90camarors

Well, as long as you made the decision for yourself, and not listen to what dennis6 had to say. Obviously one sided with faulty info. Personally, it's all preference, and give and take. I like tbi because it is so durable (and your selction of intakes to match your engine combo) and inexpensive. However, for that selection, I give up port injection which costs me some gas milage and fuel distribution.

As far as the speedo thing goes....why wouldnt it work with the 950? The signal seperates before the computer, or maybe it goes to the speedo first, then the ecm. But I know for sure it is not the other way (trust me, tried wiring the recal box right before the ecm....found out the PITA way.....)

brodyscamaro

it can work with stock from what i have read

Chuck!

Im not a tbi fan boy here, but I dont understand why you couldnt get away with a used 4bbl tbi setup? They're on ebay all the time. Even if you just get the 4bbl for ~275, which is usually teh buy it now, how much is the commander 950 computer?

At any rate, if you're looking to not spend much money look into the LT1 intake. Guys are going 8's with those, they flow OK Id probably have on on top of the lil 305 if I didnt have Vortecs.

chevypower

I'm building a 388ci now. Its going to have a 700cfm Holley 4bbl TBI thats ran by the GM ECM. I got it from Howell already wired to hook up to the factory connectors for $250, its a test model though.

Dewey316

do they need any more testers?