MPFI vs. TBI

[Guest Anonymous]

I'm putting together a motor (on paper) for my Z, and I'm pretty much sold on the Holley Commander 950, but is there a big advantage to MPFI, over the cheaper TBI? I'll most likely be bolting this onto a GMPP 33O HP Crate Engine to start out with. I was really leaning towards the more plug-and-play Ram Jet, but I know I'll end up changing cam, heads, etc. and I want the tunability of the Holley setup.

This'll be going into a mostly daily driver, fun street car. No real drag racing. I really want somethign drivable, but able to hold it's own (and then some) against the rice boys and neuspeed sticker crowd.

 

Thanks,

Henry

[Tim240z]

able to hold it's own (and then some) against the rice boys and neuspeed sticker crowd

Not an issue....just about any (even relatively low hp) V8 will kill the imports.

The MPFI will meter the fuel more precisely.

Tim

[Guest the_dj]

able to hold it's own (and then some) against the rice boys and neuspeed sticker crowd.

Just curious, have you ever been in a V8 Z? My engine is a virtually stock low performance V8, and I'm thinking about doing a couple things to it. But I'm trying to finish off the Vipers, heads/cam/etc F-bods, and blown stangs and f-bods, not ricers. The HO 330 should be good for mid-12's in the 1/4 mile at worst in stock form. You won't find very many 14 second imports, and virtually no 12 second ones. Well done turbo imports put them in 12's, and not much else does. Even the new NSX runs mid 13's, and that's considered a fast import. The BMW M5 runs 12's with its 500hp powerplant.

 

Don't worry...ricers will be history. If your modding things, shoot for the higher classes: Vipers, Z06, lambo, ferrari, etc.

 

Sam

[Guest Anonymous]

not to add feul to the fire but many full bodied dsm awd 4 cyl's are in 10's

[Guest JAMIE T]

Those DSMs are few and far between. Besides, when you come across a 10sec. Talon, you'll know it. Not every DSM is built by Excessive. Plus they will likely break a halfshaft, or other parts that the heavy hitters carry a couple of extras with them to race events. I help out(fabrication) at a local tuner shop with a chassis dyno. I've seen plenty of heavy hitter imports, and the only one that even comes close to a built V8Z is a 600HP Supra. We have been working on a '92 Talon AWD TSI. We've built a motor for it and it's getting a BIG turbo and plenty of other go fast goodies, BUT, if the owner EVER wants to go toe-to-toe with my V8Z, he can bring it on . Now with saying that, I have watched Excessive's white, trible graphic'ed BEAST in action. It leaves the line soft, but when he goes to the trigger in second gear, it explodes down the track. It also breaks something everytime he does it. I wont pick on that DSM

[Guest Anonymous]

i hear ya there. i own a talon and its nowhere near a ten sec car. personally i think its impractical to build turbo hondas and whatnot..... some people just have way too much money!

[silicone boy]

I recently mulled this question over for about 4 months. I started out by thinking TBI would be OK, but really, it's the equivalent of a great carb. I got talked into MPFI and I had my eye on the Holley system with the Commander 950. Either that or a TPI with an accel DFI. Then I got moved upscale to the Electromotive TEC3.It really set me back quite a bit more than the Holley, and the worst part about it is, the intake, fuel rails, etc. are from Holley! The big advantage with the TEC3 however is the direct fire ignition. You basically chuck the distributor for a high voltage crank fired unit. Whatever you chose, the MPFI route will give lots of flexibility if you decide to add lots of goodies on (bigger cam, better heads, nitrous, forced induction, etc). I'm saying that because I have a Z with about the same horsepower, and it doesn't really feel all that fast to me. Sure, it might run low 13's, but it doesn't feel all that fast. As many have seen with their projects, they tend to spiral out of control.

[danj]

I am also considering the Holley Commander 950 due to hood clearance problems we have run into with the 383 stroker and Air gap intake in my 83 ZXT. I don't know if it would increase Torgue/HP but the low profile and tunability of the Holley TPI is what caught my interest. I think the cost of that system is about $2,150 or so. What are the advantages and cost of the MPFI systems?

 

Dan H

[Guest greimann]

Getting back to Mr. N.T. Dumb's question about comparing and contrasting TBI vs MPFI, the differences are subtle. MPFI will give you better idle, especially on lumpy cams where idle velocity is slow and you don't have to worry about wet flow to the cylinders. Mild cams (like the one in the crate motor mentioned) will idle and run just fine on a less expensive TBI. You could also expect to get slightly better fuel mileage because of the more precise delivery with MPFI.

 

I have been running a Holley TBI for quite sometime on a cam with a little more duration than in the mentioned crate motor and am very pleased with the idle quality and drivability. I would do the TBI again in a heartbeat (of America!). I think it is a great value, and much better than a carb, which just sucks (pun intended).

[Guest Drewz]

I agree the MPFI is better on economy but the other differences are minor. I am running dual TBI's on a low rise dual four manifold with a 292 520 cam and with a few minor tweaks it idles fine and I should be at the 1/4 next month to try it out. The TBI $$$$$ difference is my main concern but if i made big bucks I would go MPFI only if the spare$$$$$ were laying around IMO as usual

[silicone boy]

I think the last two posts are right. As I said, I kind of got seduced by MPFI and I had the extra cash lying around. By the time all was said and done, I paid almost as much as I did for the entire car in the first place. . The TBI would have been just fine--it does give away some in the low end torque department, but I think the differences would be hard to notice in a daily driver. Besides, if you look on ebay, Holley TBI units are always on sale for about the same price as a good carb. For everyday use, they are fine. On the other hand, I don't regret my TEC3 purchase despite the steep price. I'll learn tons about fuel injection and I can tune it for just about any application

[Guest Anonymous]

Thanks for the great info, guys. For my purposes, it sounds like TBI will do just fine. I didn't know the MPFI was that spendy, or I probably wouldn't have considered it. I don't want to spend more on my fuel injection that on the rest of the engine.

 

Thanks again,

Henry

 

edit: oops, forgot to ask - Where is the best ($$$) place to pick up a Holley TBI system? Summit?

[silicone boy]

Like I said, you might want to look on Ebay first, cause there are a lot of systems available for great prices. If you want to go new, either Summit or Jeg's carry what you need for about $1300.

[Guest Drewz]

If you can't find a reasonable kit price let me know as a guy north of me builds them......he scratch built mine