355 throttle bodies on 348 project

TB's are 45 mm, center-to-center is identical, don't know flow rate. I'm guessing the injectors are fairly well matched to the engine size and airflow with the variable being camshaft duration. If the limits in the brain are enough, I think the oxygen sensor will take up any slack in the mixture. If the mixture is too rich (the most likely negative variable), then I'll change back to the 348 injectors. I'll be glad to measure the centers if you need it. Whaddyathink?
Nice engine in your profile, by the way.

 

I LOVE IT!

I'm comming down next week Plugs. I'll call you today to work out the time. If I remember correctly I saw this same settup on a Japanese (?) 348. The only thing different that they did was having the TBs switched around so that the plenum tops were closer together, instead of sitting out near the cam covers.

As for getting more hp, I won't doubt you'll pick up at least 40-50 more ponies. There is no way that you are going to make 80 more hp by increasing the displacement of the engine 0.1 liters. The bore stayed the same and they increase the stroke just a hair, but even then the displacement still only went up 0.1. I really feel Ferrari got the extra power by making it breath better. Just look at how much bigger the top of the plenum is compaired to the plenum on a 348, WAAAAY bigger. Then add to that individual throttles on top of each port.

 

Just for grins, here's a pic of the inside of a 355 airbox showing the velicity stacks contained within. Beautiful, huh? They're sitting on top of the 348 stuff. The stacks on in a 348 plenum are about 1/2 that size-or less. 348 has 2 54mm throttle bodies vs 355 with 8 45mm tbs.
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The entire stock 355 assembly when using an adapter 1" thick between the head and throttle bodies is about 1.5" too high to fit under the bonnet, so I have a few alternatives. 1. I can space the bonnet up enough to clear the 355 airboxes. No question in my mind that the 355 stuff with my stock mafs will work ok. 2. I can use the base of the 355 boxes as stacks and a manifold for the map. This involves skipping my "stage 1" and going directly to what I really want-more horsepower and 8 velocity stacks looking like Webers or Hilborns on top of the motor. My current thinking is #2, since the only potential wasted money is for a couple of GM map sensors. There's a very interesting discussion of maps, mafs, and engine management in the technical thread "MAF vs. MAP"

 

You want your TB's open to the atmosphere so that you get maximum air intake. But then it becomes problematic to get a MAP reading as each TB essentially becomes its own "M"anifold, giving you 8 potentially unique MAP readings.

Because the MAP readings are innaccurate (uniquely different readings is problematic) for an 8 tb setup, the MAP setup becomes less desireable for an 8 tb car.

If you throw out the MAP idea and unplug the MAFS, then the stock Motronic 2.7 is going to revert to its on-chip stored fuel-air table.

Interestingly enough, that's what our stock Motronic 2.7 ECU's already do for us at Wide-Open-Throttle; the MAF and O2 readings are ignored at WOT.

What you need is for that WOT table to be modified to squirt more fuel because you are increasing airflow.

At partial throttle, Motronic 2.7 has an Alpha-n table that stores MAF values measured by Ferrari on a dyno...in this way our cars still run "pretty well" even if we lose one or both MAFs because Motronic goes to that stored table of MAF values to replace the missing MAF inputs...and since Ferrari already measured several dozen MAF values based on rpm, Motronic 2.7 doesn't suffer much if any at partial throttle with no MAF inputs.

So to me you are putting the cart before the horse by thinking about buying MAP sensors and other add-ons. You've got to get your engine configured physically, then see how stock Motronic adapts to it for idle, partial throttle, and WOT.

Then we just need to modify the appropriate on-chip tables such that you get max hp and driveability without the MAFs. That should take a bit of trial and error on a dyno with a wideband O2 stuck up the appropriate tailpipes.

 

So, I've over-complicated it? That would be good news.

 

Yup, but you're in good company. Ferrari overcomplicated that setup when they put it into the 5 valve per cylinder 355.

 

Here's a pic of the throttle bellcrank installed (on the spare motor to be transferred to the motor in the car when all's complete). I made it from an ordinary piece of aluminum strap 1"x3/16" from the hardware store and used the pivot and bellcrank from the 355. If the return springs on the tbs aren't strong enough to do the job, I'll have touse an ordinary throttle return spring instead of the cylindrical one due to clearance issues. Note that it's about 1/2" rearward of stock 355 location, so I expect to be able to use a 355 throttle cable. I'll update if not. It's bolted to the existing bosses on the manifold. Note also my high-tech intake manifold adapter mockups built from the finest 1x2 ash available at OSH. The adapters will be 1" high, so this allows me to build the other stuff while I wait for the machinist to get to the real thing. Somebody suggested I might use Delrin for the adapters instead of aluminum. I've already bought the aluminum, so I think I'll stay with that, but the idea is intriguing, especially for its light weight and ease of working. Any thoughts? Next up is injector stacks from Hilborn-they have some that are 1 13/16"-almost exactly 45mm.
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Also, thanks, Ernie, for stopping by yesterday and sharing your ideas! It's a great help to hear from others with a new perspective. I'll give you credit for them when they work out, but I'll wait til then so you don't get blamed for any that don't! STOOGES RULE!

 

Great pics Bruce!!! Delrin is not as easy to work with as one might think. It tends to distort when you are trying to cut it. It is very slippery so one needs "very sharp" high speed tooling. Waterjet will work though. Are the two mating interfaces parallel?

 

How do you guys think up this amazing crap, and how do you have the time to do all of this?

This is amazing.

Is this going to work, and what will be the benefits of all this work?

 

That look is so clean. 348 engines should have all been built like that.

 

The mating surfaces are parallel.
Obsessive-compulsive disorder and self-employment with a bias toward recreation make time for doing it. Also, no wife.

 

Ha! Michelotto thought this up. This is what Michelotto did to make the 348 Competizione LM's from otherwise stock 348's.

These race improvements were then incorporated into the 355; hence, 8 throttle bodies on the 355.

Two different fchatters have already done this: Andy Hls personally and (I think) lndshrk professionally.

Both saw OEM 348 engines bumped above 400hp.

 

400 HP from a 348?

How do you keep tires on those cars?

If this has been done before then why so much experimentation by Plugzit?

Why didn't Ferrari do this? Smog problems? Are these things legal in Calif?

I am always inquisitive for a clever project, but I don't have the time at the moment. So, I am just looking down the road a bit.

So, if these mods work, where's the "how to do it" book, and where do you get everything w/o reinventing the wheel?

This reminds me of what Scott did with the turbo on his Mondial. You have to see that one!

 

Ferrari did it. Well, they contracted out all of their 348 Competizione LM models to Michelotto, but those cars were sold to the public by Ferrari.

There's no "how to" book yet, but there will be. I'm doing the chips for Plugzit's ECUs, he's doing the mechanical work, and the combination will be available to all 348 Brothers after he's got her driving well.

It just costs $8 for the chips, so I'll give those away for free for those who are doing this mod...and Bruce/Plugzit is compiling a parts list for what is needed.

 

Amazing w/o a doubt. (no pun intended)

Have you guys considered helping NASA?

Why not do trick ECU's for the 360 as well?

 

400 HP from a 348?
The 348 is restricted by 2 54mm throttle bodies. The amount of horsepower you make is determined by the amount of properly mixed air-fuel mixture you can take in and burn. More air+more fue=more horsepower. 8 45mm tbs allow much more air, therefore much more fuel, in. There's a lot more to it than that, but them's the basics.

If this has been done before then why so much experimentation by Plugzit?
I'm using the parts that were available cheaply ($975 on ebay) to do the job. Andy had the luxury of a much larger budget. In large part, though, I'm copying him.

Why didn't Ferrari do this? Smog problems? Are these things legal in Calif?
We'll see how clean it runs. That's part of the challenge. No Doubt (another Stooge, I might add ) is working on the computer changes. The Brotherhood is strong! Usually updates like this can be taken to the referee and approved. I've done that with a Jeep before, changing from carburetion to fuel injection using largely factory parts.

So, if these mods work, where's the "how to do it" book, and where do you get everything w/o reinventing the wheel?
The book is right here! We're writing it!

 

Naw Man...your 360 is F I N E as is already.

But our street 348's need to live up to the 348 Le Mans race heritage. Michelotto showed the way.

 

Ok, I'll buy a copy.

Sign me up.

How much?

 

This thread has really grabbed my interest. I love the strakes on the 348 and think the styling is too soft on the 355 for my taste. If you could get the HP of a 355 in a 348 that'd be something else.

Can't wait to see how it works out.

 

Stooges rule!

 

"No Doubt" they do!

If this is the 3rd such project, does this make it the three stooges?

 

Stooges-
Fatbillybob, Ernie, Plugzit, & No Doubt
that's Moe, Curly, Larry & Shemp

 

Go stooges, sounds like a great idea to me, consider me a clone.