348 engine side air Intakes

There are side air intakes on the 348 via a 3" hose to the air box

 

The existing intakes are scoops, just integrated into the window surround. If you cover them I would guess it would reduce airflow not increase it, plus they would look weird and probably obstruct visibility out of the corner windows.

 

We had been wondering about this and I was working on a mock up of an inset type. First you lose whatever visibility there is out of the rear quarter window. Next the air flow is subject to the circuitous path of the "dryer" hose, air box and pre-intake system. Lastly you can't get a handle on best case performance enhancements without doing a bunch of other things. If there is any gain it would be at speed and none of us are racing these cars. I have not seen a race 348 or 355 with this type of mod so it figures someone else has explored and discounted the mod. Might look cool though.

 

I noted the Enzo mule 348 had extra scoop by the quarter window where the intake begins. At some speed (I dunno what speed, but it aint 200) positive pressure is created in the system, which can't do anything but help. The more air you can cram in, the more hp. Makes total sense to me. "Course, I'm no expert. But I like the idea. Make 2 sets.

 

(Ahem, cough, cough) Somebody looking over your shoulder, Vince????

 

The additional scoop on the Enzo test mule does not appear to be for the engine intake, I'd say it's actually to feed air to an oil cooler somewhere (possibly for a transmission cooler).

Looking at various pictures of the Enzo test mule, it appears that the standard 348 style intakes were more than capable of feeding the engine with air without the need for extra scoops.

As for "cramming more air in", the air filter is going to be a major limiting factor as to how much air gets to the engine.

If you're already filling the airbox easily with the standard intakes, scoops aren't really going to do anything more for you!

TBH, I suspect that adding additional scoops to the air intakes is simply a solution to a problem that doesn't really exist!
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If I remember correct positive pressure in the intake starts once the car is going over 120mph(?). Something to the tune of 1.5psi (?????)

While the extra air is good it can actually hurt hp. How? Because the Motronic is not an adaptive ECU. The full throttle mapping is open loop, meaning it ignores the sensors and uses fixed settings. I found this out after testing a modification I did a while back. The engine was sucking in so much air that it ran lean at wide open throttle, and because of that I lost power. I had no way of increasing the fuel, nor adjusting the timing, so that mod got shelved.

Unless you are going to be able to tune the fuel and timing for the extra air it's "kind of" wasted.

 

I am with Ernie.. I also lost a little power in the upper rpm's testing a mod.

 

Hi Ernie. True if it was speed density but mass airflow car can compensate for small increases in airflow (maf reads higher g/sec and fueling increases as a result)

Unless you are saying Motrinic ignores the maf sensors at wot? I would find that odd but even if so, factory calibrations usually are rich enough that a bit of extra airflow wouldn't reduce power.

 

Just about ever car make goes in some type of open loop setup and doesn't care about anything but water temp, IAT, and knock.... that's about it.. differently does not care about a maf which is only used to get the most MPGs out of a car... which is why i roll speed density on my blower cars..haha

 

Yes. Thats what he's saying. Pretty much all MAF systems still have wide open throttle as a solid set map. No learned adjustments. Set in stone.

 

Not any car that I've seen. Open loop just means it's not using narrowband o2 sensor feedback, not that all other sensors are ignored. (though some cars with factory wideband will use o2's at WOT).

Every car I tune with a MAF (admittedly all GM's) use the MAF at WOT and a blend of VE/MAF below a certain rpm for fast transients. It will use the map sensor as well.

After setting power enrichment table to desired air fuel ratio vs rpm (entered past a certain tps/rpm/load but certainly at WOT) the MAF is disabled so the VE table can be dialed in. Once the VE table is tuned you adjust the maf table until part throttle fuel trims are slightly negative and commanded air fuel matches actual air fuel in power enrichment mode.

I too prefer speed density on forced induction cars (which will be primarily be using the VE table for fueling, MAP vs RPM) as the maf sensor maxes out very fast on those setups.

 

Not learned but any additional airflow (up to a point) will be read by the maf sensor and compensated for.

It's not 'learning' just that fueling will increase if the maf reads another 20grams/sec for example. Just as fueling would decrease with clogged air filters as maf output would be lower.

Again, this is true for any car that I've ever dealt with and would be surprised if motronic cars do not reference the maf at wot but I'm not entirely sure.

Even if it went into speed density mode (which I doubt), it would still reference the map sensor which can read a handful of Kpa above atmospheric pressure.

 

Question, is there not a fuel pressure regulator adjuster? I thought I saw something like that in an earlier thread. Wouldn't that compensate somewhat for more airflow?

 

If its adjustable it can add fuel at wot but not a good solution as it throws the rest of the tune off. (Would be very rich in open loop at cold start until o2's could drive down fuel trims in closed loop)

 

Guess I never threw in my .02 on this but I think the factory setup is excellent. Would bigger scoops increase performance? (possibly higher airflow but increased drag).

I highly doubt it would be worth the effort but you would have to measure performance and monitor air fuel ratio to validate.

 

You can get the same effect by placing a small wing (or spoiler) over the back end of the top (ala 328) to create a small low pressure region over the engine bay.

 

Yup that is what I'm saying. The Motronic 2.7 ignores the Maf and O2 at WOT. The factory calibrations aren't very rich at all at WOT. Matter of fact my car is right around 13:1-ish afr at wot with the current mods I'm running. The modification I test which resulted in a loss of power the afr was over 14:1 the entire time. There was a "richening up" in the midrange from about 14.7:1 in the low end, "down" to 14.2:1 in the mid range, do to the stock mapping adding more fuel. I tried in vane to richen it up. The MAFs got dialed down from 383 ohms to 150 ohms, did another pull, then down to 0 ohms did another pull and it didn't do jack squat. The afr remained over 14:1 all the way to the rev limiter. So I know first hand for a fact the Motronic ignores the maf at wot.

After that round of failed testing I put back on my previous setup. The Motronic is OBD1, so it has to be opened up for any tuning to be performed. The EPROM removed and an emulator put in it's place. Tuning performed then the new mapping burned to a EPROM. The other trick is the 348s have TWO ECUs, one for each bank. You you have to be able to tune each bank independently, yet at the same time while on the dyno.

So while adding scoops to the corner window intakes may be a way to get extra air to the engine, in order to take advantage of it you MUST be able to add more fuel if it is to yield any kind of extra power. The Motronic will not do that on it's own a WOT.

 

No.

The stock FPRs are not adjustable.

However there is a difference between the different years. Early 348s run 3bar regulators while later 348s (spiders, SS, GTB/S/C) run 3.8bar regulators. So you can richen up the fuel a bit with a higher pressure regulator. I'm running the 3.8bar/55.1psi regulators in my car currently and it only gave me a bit more torque in the mid range (+2-3 lb/ft) and +1 lb/ft tq peak.

 

Guys, please don't take what I have been saying as being negative. Trust me I really want our 348s to make more power. I'm not trying to stop anyone from making mods that will increase power. What I am saying is, just be aware that you WILL have to deal with the lack of fuel, and mapping, when you make mods that yield more air.

Me, I'm currently dealing with trying to solve that issue myself.

 

Interesting! Do you happen to have a screen shot of the MAF table you were calibrating? Usually see that in g/sec vs frequency or g/sec vs volts and not resistance.

Were you able to find and tune the ve or other table used at WOT for fueling or still working on that?

 

I wish I had that info, sorry but no tables.

I didn't and currently don't have access to any of that. All the dyno pulls I have done have been performed without the ECUs hooked up to anything. They have been done with a sniffer in the tail pipe to get the ratios. I desperately want to get it actively tuned while on the dyno. The two tuners I have talked to are literally on opposite sides of the country, and one of them has only tuned the Motronic 2.7 in Porsches.

 

Come get you some!!!! this is just a test section.. i actually shift at 7700 and make some where around 26psi in the winter time.. my C5 blower car
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Yep that's making some boost. Tune that stuff every day.