duke_mushroom

I'll be starting my 383 TPI buildup in March, but I don't know which one to use. I've been w/the L03 so long the only TPI experience I have is with my bro's camaro and my dad's corvette. So basically I'm asking which one is better? Which one will give me the most out of the engine? Thanks.

nblanchard

I would have to say MAF setup... but then again.. the Accel DFI only comes in Speed Density. Definately MAF in my point of view

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
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John Millican

iTrader: (1)

Here we go again.........

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86 Camaro Sport
LT1 Induction
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Moderator at SE ThirdGen

anesthes

iTrader: (12)

Hi,

This one is pretty beaten to death.

Asside from the actual MAF sensor which I think is the biggest downfall, I think truely measuring the incoming air is the best way
to calculate a/f ratios.

Speed density is a better stock system,
But I think the speed density downfall is
its algorythms used for calculating vacume to airflow ratios, and its ability to make double the calculations per cycle in the amount of time it takes to trigger a difference in operation.

So my vote is in MAF I guess, from personal experiences.

Some chip burners may dissagree with me, perhaps they're better at calculating volumetric equivalences for their car
and cam, but whatever.

Chip burning is kinda lame anyway, I'd rather spend my money on a programable computer, with a laptop interface so I can dynamicly change variables and insert new procedure loops.

-- Joe

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1989 Formula 350 4-bolt mains, Forged .030 TRW pistons, SLP 51010 Roller Cam, Comp-cams roller lifters,
Summit 1.5 roller rockers, World Products Sportsman II 2.02/1.60 heads, Edelbrock TPI Intake,
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Since close of track : Ported SLP runners, Ported Plenum, AFPR, Autometer 100lbs F/P gauge, A/F ratio gauge, MSD 6AL.

http://www.joesperformance.com

Grim Reaper

I have worked on both in my eprom burning. First BOTH ALWAYS will benefit from an optimized eprom. Mainly because of the spark advance - on TPI cars, a couple degrees can mean the difference between an engine that behaves like a dog, runs great or detonates. Tuning your spark tables is a major part in getting the most power out of your system and BOTH need this.

For a 383, the one thing to remember is that you'll be maxing the MAF @ about 5,000 rpm. After that, the MAF is useless for any fuel compensation. And you MUST use the "%Chg AF Ratio vs RPM (in PE)" to give additional fuel, and it is basically "a shot in the dark". A WB O2 sensor is helpful here.

Adjusting the Fuel Tables on SD is easy. You just drive around, capturing data on your laptop. Then when you get home, you sort the various RPM/MAP values, determine the average BLM/INT you are running and then make corrections accordingly. Not hard at all. In fact, this is where SD has an advantage as you can change a specific RPM/Load value without affecting anything else.

With MAF, if you HAVE to adjust the MAF Scalar tables to get the fuel mixture right, you are looking at a LOT OF WORK, and, while you may fix a certain airflow value at a certain RPM, you may find that at the same airflow at another RPM, the value is off. So you have to compromise and accept that it will not be perfect in many situations.

As I said, I've worked on both and I have made both work. The area that takes MOST of the time is the "spark table" optimization (to obtain max power), and it doesn't matter which one - they are both the same and take about the same amount of time.

SD is more "reactive" (reacts quicker) than MAF, and MAF gives a more consistent reading on a "steady cruise". FYI, I know guys that have the new LT1 8051 ECM with BOTH MAF and MAP sensors. Many have found a performance increase by switching the code in the PCM to operate in SD only mode.

As for DFI, if you NEED DFI (high RPM > 7,000 or high fuel needs), that's fine - in fact, you SHOULD look at DFI. For a daily driver, it's a very expensive alternative that actually does less (functionly) than the GM eprom. Plus, if you EVER break down, good luck on finding a cheap replacement. For SD, I just go down to the local junkyard and pull the ECM out of a 3.1 Cavalier.

As I said, if I had a high rpm motor or required high fuel needs, then you really should look a DFI. But I consider it more of a "last resort" as to an "alternative". Altering on the "fly" has some advantages, but often you really need to look at a collection of data, at which point "on the fly" tuning has no advantage. But I would say MOST of my tuning requires me to look at my captured data first, so "on the fly tuning" would have had little benefit for me. But I will admit there were a few times that I would have liked to have "on the fly" tuning. Maybe one day, someone will adapt a similar "edge board" that is available on some of the other ECMs to facilitate this. But stil, for the majority of my tuning, I really needed to sit down and review ALL of my captured data before I made a change. Pretty tough to do in your car, when you are driving.

[This message has been edited by Glenn91L98GTA (edited November 28, 2001).]

85wilrocu

All I have to say is , why did chevy stop with the maf in 89? and then went to speed density? in 90-92, and then went back to maf????????

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1985 Iroc Modifications:
Ram air,K&N filters,Mas Screens off, fins taken off,52 MM Throttle body,
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Fords are Like Tampons, Every PU$$Y Has One!

Grumpy

Two words
1) Emissions
2) OBDII

Reading the protocol will show why GM did what they did for OBDII, BTW my firends LT1 runs much better in MAP mode then MAF. You can edit the PCM to do that.

Look at the CR5s (RACING), MAP.
Look at any pro racing and they are <drum roll>
MAP

Once you get the MAF sorted out CORRECTLY!! they can **ABOUT** match the MAPs, but it takes weeks more work to do so.

Grim Reaper

And most of the DFIs - MAP. I can't think of a MAF based DFI off-hand, but I am not up on my DFI systems so a few might actually exist. When you really think about it, the guys racing are already spending big bucks to go fast. With all the bucks involed, if MAF gave better results wouldn't racers be using it?

It don't accept the "cost savings" issue when you consider the bucks they've already spent and willing to spend in order to win.