355 throttle bodies on 348 project

Well it would cough/spit through the throttle-bodies at the "good to lean" transition, then just bog as the throttle continues to wide-open.

 

Well Plugz should be on later today to explain it more. I haven't been for a ride it it yet, so I can't say for sure what it's doin. The best thing would be to strap it onto a dyno, that way we can see what mixture it's running at WOT. Then from there we can adjust the mixture to the ITB's.

One thing is for sure. He did get more power just bolting the ITB's on. How much? We don't know for sure, but I will not be surprised if it's at least 50hp+.

 

Stooooooooooges rule!

Anyway, the only 355's that have the chips should be the 1995 2.7's and the Challenge variants that ran 2.7. 5.2 should be OBDII which I think is software uplink programmable rather than chip programmable...but...because the 355 has more displacement, different FPRs, different injectors, etc...I don't know that the 355 fuel maps would help us.

Also, it's going to matter where in the rpm range and throttle position that he was running lean.

IF he is running lean at partial throttle, for instance, then we're probably going to have to bump up the fuel pressure and/or go to larger injectors. The existing 2.5 and 2.7 software can compensate over a fairly wide range already at partial throttle based on the O2 feedback and MAF input.

Speaking of MAF input, is he using the 348's 2.5 MAFs or the MAFs from the 355?

IF he is just running lean at Wide Open Throttle, then it may be that simply bumping up the fuel in the chips will be fine.


Does the 2.5 have two identical ECU's like the 2.7, or did it just use one ecu to control both engine banks?

 

There's no doubt (ha ha) in my mind that he's got 50+ hp just from going to the ITB's. The project that I had in mind was removing the 348's intake air U-bend tubes to swap them each out with a cone air filter to MAF to tb (connected with cut up coolant hose and hose clamps), for instance, to get rid of the intake air bottlenecks at the 1 air filter box plus through the long, bent air intake hoses.

I may still do that project, too.

It's just so obvious that the 348 isn't getting as much air as easily as it can handle it.

Plugzit has removed the intake plenum-to-horn-to-cylinder bottlenecks as well as shortened the total length of the air intake tubes in addition to straightening those air intake tubes...so he's gone much farther than the simple project that I had in my head...but this just goes to show that the OEM 348 has many, many air intake bottlenecks that by removing we can coax out significant more hp.

 

OK. Thanks! Good to know.

 

Well maf, electrical and injector wise plugz is using everything "stock" from his 348. Though his fuel-pressure regulators are 355.

 

OK. Now we need to know where his RPMs start going lean, and at what throttle position (WOT or partial).

 

Are we 100% confident that he's getting good and proper vacuum to the 355 FPR's?

Would it be worthy experiment to temporarily disconnect the vacuum lines to the fprs to go full rich?

 

Yes, it is a short line about 3" long and plugz installed new line in that capacity.

That would be a good tell-tale at partial throttle. At WOT the fpr's should get atmospheric pressure either way. But it may be worth a try, to verify any "possible" difference at WOT.

 

Rise up the fuel pressure to 3.5 - 4.5bar and readjust the injector and ignition timings on the dyno or street with a realtime linkup to the ecu. I don't think you need bigger injectors for your setup. If you also port the heads, install bigger valves, and aggressiv cams with higher rev range then you may need some but not now.
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Samy

 

OK, excellent power at full throttle up to 5000 RPMs or excellent power at partial throttle up to 5000?

No signs of detonation, correct? No signs of the speed of the revving up decreasing, right? I.e revs just as fast or faster than before the mods, yes?

Also, did the brain re-learn give you a reasonably stable idle, and did you feel the throttle pedal stick any when revving?

Frankly, it sounds as though the system is close to handling the mod as is. We can certainly add more fuel at and above 5000 RPMs via the chip. No problem there whatsoever.

I'd like to know if the power falls off at a higher RPM when you disconnect the vacuum hoses to the FPRs...and with the FPRs in that state if the idle goes nuts (or SLOW DOWN lights kick on) or if the idle still stays reasonably stable.

 

Goth, can you explain the TPS mod to me more fully? Would there be *any* difference in the TPS signalling Wide Open Throttle with your hole-drilling-reverse-TPS mod, or are we cool there?

 

The "total" TPS rotational travel remains at just under 90 degress (stock). Though the rate of air ingestion will be higher than stock at any position above idle, because of:

1. The additional flow area of the eight TB's.

2. The fact that "atmospheric" air pressure (TB's) are/is alot closer to the intake valve area. (Stock 348 the TB is about 18" from the intake valves. Now it is about 8" from the intake valves. This was one of the reasons Ferrari went to individual TB's, one gets quicker response.)

 

Thanks. Not a problem.

 

I am actually dissapointed it is working so well up to 5000rpm. What that tells me is the 348 system is not to far away from the 355. Just because the intake can flow more does not mean the engine will flow it. It makes sence that it well but we need some hard numbers. I gave Plugzit my horsepower meter but he has not posted numbers yet so far. Stock he was at about 225 rwhp at the wheels. Goth got 315rwhp with his 355. To be cheap about it we need to wide band o2 the thing tweek maps ND style and then see what the rwhp is on the gtech meter at the least before we can really call this a success. Has anyone looked at 348/355 exhaust header differences too? You can't max the RWHP by changing intake without matching the exhaust. I am sure it is good for some HP hopefully its alot. 75hp is unrealisitc IMO otherwise Ferrari would never have made a 355 they would just put a bigger intake on a 348. They had the technology it was the 333sp and the 348 mich cars. The 355 was done for a good reason I susspect.

 

Naw...the 5 valve was an experiment. What made the hp on the 355 was the 8 tb's and slightly greater displacement. None of the 355's were hopped up to match the top 348 Competiziones (2nd and 4th in class at Le Mans, 1994) which had up to 500 hp.

Keep in mind that the 4 valve per cylinder 348 motor is the *same* engine as on the 288 GTO supercar, except with greater displacement (and no turbos). Motronic 2.5 and 2.7 is superior to the fuel injection on the 288 GTO, too (Weber-Marelli?).

Just no way that a 1987 cat (e.g. on a 288 GTO if so equipped) flows as efficiently as a 1995 348 cat, or that WM is as good as Motronic 2.5/2.7.

The 500 hp 348's had track pipes rather than cats, 8 tb's/better intake, and better chips in the Motronic 2.7. But you are still talking about a 200 hp difference from street to strip, with Normally Aspirated 348 CLM's putting out slightly more hp than the turboed 288 GTO's.

The big restriction on the 348 is the air intake. Everything else just needs a little tweaking.

 

Change the cams to use the bigger inlet manifold and get the performance up in higher revs. Only by changing the intake manifold to a bigger one you lower the intake flowvelocity that a disadvantage but now you can change cams and exhaust system to get more air flowing trough with the same speed as befor. And if only the intake manifold raise the hp up to 380hp the car won't run without recalibrating ecu maps under full throttle because it goes lean and stall.
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Samy

 

I think there is merit to what fatbilly is saying. The exhaust can definately be optimized as well. Look what paps 348 did just putting a muffler on......he added over 18 RWHP! So that alone is an indicator that changing the intake is NOT the "only" difference.

What cam profiles did the competizione have? mapping, exhaust and intake to claim 500hp? Not to mention racing fuel.

So it looks like the stooges are headed in the right direction!! Go stooges!!!!

 

Oh yeah, the stooges are headed in the right direction. The Competizione LM's did have racing exhausts, so point taken there.

I don't know what if anything the LM's changed in the cams...but the timing belt held up for 24 hours of Le Mans so they weren't running the infamous "3 hour" 348 racing timing belt and cam system.

They did, however, raise their rev limit up to 9000 RPMs. If you just took a stock 348 engine and went up to 9000 RPMs that would give you 370hp with no other changes (hp=torque*RPMs/5252).

Since the 348 CLM's ranged from 360 hp up to 500 hp, all with a 9000 RPM redline, that hints to me that they tried cam settings/profiles that went from having less torque than a stock 348 (especially considering their race exhausts and 8 tb intakes) up to having a fair amount more torque than stock.

Which is to say, Plugzit's stock 348 cams are already in the range of cams used in the 348 Competizione LM's.

If the 8 tb intake and race exhaust gives 10% more torque in sum, then raising the rev limit to the 9000 RPM CLM level would, on paper, hint at 412.5 hp without changing cam profiles or pulley settings.

...and I think that's conservative as to how much better those 8 tb's are flowing extra air over the stock 2 tb intake.

Bump up the fuel to match, and then even without changing the ignition Advance (he's not running race fuel, after all) you've got yourself a 400+hp 348. Same cams. Same ignition advance. More fuel. More air.

 

400hp??? I would be happy to have that!!! Have you experimented with 355 tunning?

 

Way out of my league, man!

 

Awe c'mon ND! Help a brother in need.... (in need of more HP !!)

You know ND I was looking at the size of the runners on the 348 and they are not too different than the 355's in size. I am hinting that if one even puts larger "stock style" throttle boddies in the 348 manifolds, one would be able to see significant gains too. What do you think?

 

Well, the stock 348 "2 tb" system is still too far apart from the cylinders, and still goes through those tiny horns from the stock intake down to the cylinders.

Would you get some gains from larger tb's in the existing 2 tb system? Yes, probably, but you won't see the throttle response and you won't see the performance gains that Plugzit will see by going to 8 tb's that are closer to the cylinders and that have larger pathways than the stock horns.

Likewise, I'll get some gains from going to a short, straight path cone to MAF to stock tb on each side, as that will shorten and straighten the intake tube length (get rid of those U-turn black intake tubes!)...but since the tb's are still a long way from the cylinders, and since the intake horns down to the cylinder are still so small, there's just no way that this change will match Plugzit's 8 tb mod.

 

I agree the stock 348 horns are very primitive. Though the 360/430 have their TB's "far away". So I would think it is the horn design, small plenum and small TB's that may be the biggest restriction. I agree the rest of the intake (B4 TB's) is not helping either. Here is a pic of the inside of a 360 intake:
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