4.3 cpi vs tbi

hi guys , i have a 92 jimmy with the cp4.3 i am gettting a 91 blazer with a 4.3 tbi either stronger? how about gas mileage ? thanks STILETTTO

the cpi 4.3l will be more powerfull. better milage to as long as it is working properly

Hi John, well that sounds like a bummer, as i am retiring my jimmy with the 4.3 cpi for a blazer w/4.3 tbi. are the mpgs even close or anyone have the ratings? hp and mpgs. i test drove a 91 jimmy with the 4.3 tbi amd thought something was wrong with it since it seemed hardly to pick up, while my jimmy can get a baby chirp at 2nd both are automatics thanks Stiletto

TBI's have 40 less hp.

You won't be happy.

4.3 CPI was approx 190HP. 4.3 TBI was approx 150HP if I recall correctly. My 93 CPI was MUCH faster than my 89 TBI. Many differences. As for fuel mileage, my 89 TBI got MUCH better mileage. It's a tossup, what are your needs? Towing anything? Highway driving? City driving? My 89 was fine in the city. On the highway, if there was any wind, the speed limit of 100KM/hr is about all you can do.

They both get the same mileage. No different fuel consumption if they are both properly maintained.

hi and thank you much! i am short on $ and i found a 91 4 wheel drive for $900 it has 180,000 miles on it if i could find another i would i haven/t baught it yet . but tbi is still a vortech? good if not abused for 300,000 ? thanks Richard

also simply city driving and work and snow ! i get about 20 mpgs with my 92 cpi jimmy taking off nice and gentle hope the blazer 91 tbi comes close if i get it.

it might if you tune it up, but with the less horsepower, it will be working harder for the same performance.

I have an 89' model how do i tell what type of 4.3 ltr is in it?

thnx

Just found the answer...


its a tbi

92-95 were the only years that had the optional high output cpi 4.3L.

My 93 S-10 4.3L CPI is much stronger than my 2000 Jimmy SLE. I thought something was wrong with the Jimmy, my Stealer blamed it on the difference in the Rear-end Ratio. Now I know. Thanks. Oh BTW, the gas Milage between the two is pretty darn close.

The dual plenum design with the CPI system really helps higher rpm torque.

thanks! well the guy who was slling me the tbi blazer hasn/t called me back so i'm still hunting for one! cpi or tbi seems not much the difference . my camaros are my race cars the soon to be blazer/jimmy is just to get through the michigan winter and work ! Most Sincerely, Stilleto

Trust me!

Get the CPI! The TBI is a gutless pig next to the CPI engine.

Don't waste your time with a TBI.

possably the 91 4x4 tbi still hasn/t returned email nor phone calls , til i sell the 81 z28 or my 97 funds are far two unavalable for a real choice of one otherwise i jump for the 96 style they look awesome in black though a hottie down my street drives a white one !

I *know* we have been over this before.

The first offering of CPI motors had a few more hp, later ones a bit more than that. the base TBI motor was 160hp.

(forgetting of course that the 4.3 should have never been shoehorned in this vehicle, the 3.1 and later 3.4 MFI versions should have been used, culminating with the 3.9 but I digress)

both are dogs with different fleas.

I myself, prefer the TBI units over CPI for a number of reasons:

the tbi system is the easiest thing to work on or modify on the planet. I would sooner retrofit a TBI system to a 1960's muscle car than try to set the jetting on a holley.

the tbi system is also CHEAP. parts are a dime a dozen and you dont need a degree in nuculear engineering to replace them. (most common failure: EGR, tbi:$45, cpi: $187)

tbi equipped blahzers are hard to work on, the cpi units are impossible

a good running tpi unit will return 21-22 mpg in a 3.42 axle blahzer, and 18-19 when it goes sour. a good running cpi unit will give 21-22 and 12 when it goes sour, which given it has 4 O2S's to work with, is apparently every other week.

It might be because of where my shop is, but I see a lot of blahzers. the tbis are always easy to get going, the cpi ones require twice as much time. and I happen to have the proper scan tools.

CPI is bullet proof and much more powerful than the TBI.

The ony CPI downfall is the poor initial injector that was flawed. Once replaced, it can't be touched.

Plus, the Dual upper plenum design and IMTV (Intake Manifold Tuning Valve) allows for the torque curve to be moved to the higher rpms.

Esentially, you get no torque loss through acceleration.

that would be the first time in automotive history that the words 'bulletproof' and 'cpi' appeared in the same sentence.

there is not enuf space here for me to detail all of the 'will occur' failures the cpi motor will face, let alone the 'probably will occur' failures. suffice to say, the design was hideous, the use of 'space age' materials was foolhardy and when they fail, they become bombs (literally) Ill pass. Im tired of coming across W code blahzers with more fuel in the oil than in the tank

please note, the power increases of the cpi motor vs tbi motor have nothing to do with the injection system per se.

by individually metering fuel, emissions were improved such that different heads and camshaft were able to be used. and thus got more power. you can put in a better cam and intake on a stock tbi and make more power than a cpi AND be able to get it to run with no SES

As I said and as you obviously missed, when the injection system is replaced with the newer improved unit with the new nut kit, the CPI blazer is much more advanced and powerfull than any TBI.

I'll take powerful.

You can take simple and gutless.

well i see i started a war cpi vs tbi, yes my jimmy 92 cpi i can get 20 mpg city aslong as i take off gentil my digital dash bites all left is speedo and odometer had the cpi go bad $500 quote but my new mechanic Hank AT HANKS AUTO IN MT CLEMENS MICHIGAN REPLACED THE THEN LEAKING GAS LINES-$180 EXHAUST STUNK TO HIGH HEAVEN CUZ OF THE GAS IN THE EXHAUST .MPG DROPPED TO 5 PER GALLON OTHER THAN THAT THOUGH CPI ACTED GOOD AFTER THAT ! ANYONE GOT ONE FOR ABOUT A GRAND ? 2 DOOR 4X4 AND SPARE ON TAILGATE ALL THAT MATTERS ANY COLOR EXCEPT PINK IF THERE IS ONE, SINCERELY, STILETTO

You should wonder why GM switched back to the TBI design and still used it in my 1999 Bravada 4.3L... my friend has a 4.3L CPI and it's a torquey SOB; however, it's been nothing but problamatic for him - left him stranded a few times too. Have you checked inside the manifold on the CPI? It's a cluster f*ck... poor design, but nice on power; it's a shame they didn't spend the time to properly design the delivery system inside the manifold.

I would have to agree w/ Blazer LT, after replacing my nut kit and spider, my 94 cpi is a bull in a china shop! My buddie's 2002 s10 4 door pickup is crawling when we are tooling down the hiway, and as far as pulling, it limps up hill w/ 16' fiberglass tri hull, mine barely notices that it is there.

I would have to agree w/ Blazert LT, after replacing my nut kit and spider, my 94 cpi is a bull in a china shop! My buddie's 2002 s10 4 door pickup is crawling when we are tooling down the hiway, and as far as pulling, it limps up hill w/ 16' fiberglass tri hull, mine barely notices that it is there.

Blazer94, what did you replace the spider with, a new stock manifold or different manifold design altogether, or just the clutter inside the manifold? My buddy is looking to get rid of his - he likes the power of the CPI but because of the manifold he was even thinking about going carbueretor route.

Blazer94, what did you replace the spider with, a new stock manifold or different manifold design altogether, or just the clutter inside the manifold? My buddy is looking to get rid of his - he likes the power of the CPI but because of the manifold he was even thinking about going carbueretor route.

1999 Bravada, I replaced the injector harness and regulator , nut kit assembly, (parts from Linder Tech services, www.lindertech.com) cleaned the plenum,egr valve, and new fuel pump.110,000 miles and is running like almost new. ( slight leak in exhaust manifold, will get to that later.)

You should wonder why GM switched back to the TBI design and still used it in my 1999 Bravada 4.3L... my friend has a 4.3L CPI and it's a torquey SOB; however, it's been nothing but problamatic for him - left him stranded a few times too. Have you checked inside the manifold on the CPI? It's a cluster f*ck... poor design, but nice on power; it's a shame they didn't spend the time to properly design the delivery system inside the manifold.

They didn't go back to TBI, they went to CSFI which is completely different than TBI and more closer to the CPI setup.

The CPI was not killed due to problems, it was just too complicated and expensive to make. And the design is still one of the best plenums made since the 70s.

Yeah, what about 96+ csfi? I have that, have the extra horsepower, minus all these problems. It seems that the csfi fixing is cheaper because you don't need to replace a whole injector spider, but instead individual injectors.

Are the 96+ csfi's a better platform for supercharging because of their "more advanced" fuel control? Are these injectors better under boost?

Yeah, what about 96+ csfi? I have that, have the extra horsepower, minus all these problems. It seems that the csfi fixing is cheaper because you don't need to replace a whole injector spider, but instead individual injectors.

Are the 96+ csfi's a better platform for supercharging because of their "more advanced" fuel control? Are these injectors better under boost?

Actually, the CSFI has 5-10 less horsepower than the CPI and 10-20ft/lbs les toques but the differences could no be really noticed.

The CSFI is indeed cheaper seeing you can swap out one poppet valve if it sticks instead of changing out the whole injector. But the CSFI has its problems also.

That nice-looking two-piece aluminum intake CPI manifold is interesting. There's a separate plenum for each bank fed from the throttle by zip tubes. Between the plenums there's a passage that can be opened or closed by the IMTV (Intake Manifold Tuning Valve). Without going into all the engineering niceties of tuning and Helmholtz resonance, the idea is to boost output during the mid-range without losing torque at the bottom.

The IMTV relay is mounted on the firewall and gets its signal from the ECM (Electronic Control Module). It turns on at 3,025-4,650 rpm with a throttle angle of above 36 deg., and off below 2,975 rpm or 34 throttle degrees, or if rpm exceeds 4,650.

The IMTV valve will open allowing for a more efficient airflow path at higher RPMS and therefore move the torque up into the higher rpms.

In essence you can have all the torque at low rpms and at high rpms at the same time.

Pretty ingenious if you tell me.

Is that IMTV with the csfi? I had never heard of that before, but it sounds really cool. hahaha you sort of lost me there.

So you don't think there'd be any advantages to supercharging a 95 cpi vs. a 96 csfi?

Oh, I'm sorry, I forgot to answer that question.

1996+ are the only ones you can actually supercharge.

There are basically no supercharging options for the CPI 4.3L.

Thanks for the answer, even though it seems like such a teenager question. I'm trying to figure out if our stock sensors and computer need to be modified much to do one of these upgrades.

I've been trying to troubleshoot my friends turbocivic and have been learning a lot about how to do this stuff. His stock MAP would only read up to 7 lbs of boost and his computer was not adjusting well. Will out MAF detect forced induction properly?

It should.

Most superchargers for the 4.3L are only at 5psi or so.

the 4.3 cpi is a stronger motor, however the tbi isnt all that bad, it comes with 160 stock hp, but mine is more i think, i have a 91 blazer with the tbi and it runs well with a edelbrock intake manifold, holly throttle body and a borla exhaust. but gas milage isnt as good i dont think.