AUSSIE TUNER

Hi guys,

Love this site & looking forward to spending more time on it.
Just wanted to see if any of you guys had an opinion on this topic.I'm sure it's been spoken about many times.We have a huge debate on our Australian LS1 site at the moment(us agains't them),most of the top tuners over here prefer to tune in SD (removing the MAF) & say that there is no better way.At my shop using edit of course I prefer to use a maf.My argument is that from what I can see you guys over here seem to use mafs with great success & at this point in time are well ahead of us on the track also,I have heard comments that anger me such as "they can't tune the LS1 in SD over there anyway" & I've had to remind them where the LS1 came from in the first place.From my experience in testing using a HSV 300 (c4b) ve cal as a starting point (limited addition Holden special vehicles car which runs no maf from factory ) & tuning with VE I have found that there seems to be no evidence of an increase in power on my dyno by removing the maf especially in stock to mild applications.I have seen map readings in the region of 102 on EFI Live with a stock maf which indicates to me that there is little restriction & found that while tuning without a maf in SD mode that ignition timing was inconsistant at higher rpm.In my language the maf allows an accurate measurement of air flow while SD is only an estimate,I can't see why you would want to step backawards in time & technology.Does anyone know the maximum HP that a stock maf will support.We have seen 485 corrected HP/495ft/pounds through a stock Maf on COME Racings superflow engine dyno with our mild 218/222@50-114 382 COME stroker.

Any thoughts?
Regards Glenn

ChrisB

I think the MAF is definitely the way to go if you can get it to work. Now no doubt that SD setup can run well, but I would still submit that under a variatey of conditions the MAF will come out superiour in drivability, etc. as well as virtually the same in power.

The potential advantages I see for SD are

1) Removing the MAF - "restriction" issues

2) Response time lag (mostly on FI cars with the maf on the intake side).

3) Freedom in routing the intake tract.

A for #1, the maf being a "restriction" - it depends on how much power you are making. On a stock or heads/cam car I don't think it is an issue at all. As for how much power the maf will "support" - well, you can flow as much air as you want through it, as the maf starts becoming a restriction you will just get a larger pressure drop. It's not that you will simply rail out at a certain point. Now as far as air metering, it will max out somewhere from 450-500rwhp normally (depending on your bsac, etc.) - you can easily tune past this point - it will be the same as tuning a SD car at WOT at that point anyway - use the PE vs RPM.

As for #2 I would keep the maf as close to the TB as possible - again, mainly an issue of FI setups. I would just move it to the pressure side. That way you can run a normal BOV also.

As for #3, well - if your intake prevents you from using a maf at all, then you are doing SD - but in a vehicle whose configuration allows for a MAF I would go for it.

Bink

Do you think the C4B tune would help a car with 475+ Crank HP???
Very interesting thread.

ChrisB - I'm pretty much FI stupid...but I guess the Maf is valuable at low pressure/boost. So, assuming that's correct- please correct me if it's not- does the MAF need to be rescaled for use with FI?? Just curious.

joel

AUSSIE TUNER

Thanks Chris,it's guys like you with your help & advice that make this site what it is today.Our problem with our cars over here is that our mafs are approx 18 inches away from the TB.My next test will be to try and squeeze them in front of the TB & then I will try to squeeze in a nice straight intake.Our intakes run at a right angle off the TB with an air box in th LH front corner of the engine bay.I'm not sure if your latest Australian built GTO has the same deal.We have a room problem but I suppose were theres a will theres a way.The mafless SD LS1 tunes I have driven feel a bit more response & a little angrier of idle but I suppose thats due to the delay with our maf placement so far down the intake track,maybe a maf will never duplicate that response,I won't know until we move them upstream I suppose.
Regards Glenn

AUSSIE TUNER

Hi Joel,from my testing I am yet to prove it but I must admit that with LS1 edit I did have inconsistant ign timing in the top for example from 5000-6000 I saw 20-24 degrees spasmotically,it wouldnt hold a good stable 24 degrees as targeted in the tables in the top end,maybe this a VE issue or maybe there is not enough accessable tables in LS1 edit to cater for accurate SD tuning,I asked Carputor about it & they couldnt help me,maybe someone else might have idea but still to abswer you question with an angine producing similar HP while seeing good ign timing & air fuel ratio's at a given point we saw no increase in power over the maf.Other tuners claim a bigger difference (up to 30-40 hp on a stock engine over here but I just beleive that in most cases that the maf tune wasn't good enough in the first place.Maybe I'm doing something wrong but I doubt it,I've been around for a little while.This is what my debate is all about over here at the moment,I think some people are getting a little carried away.Our stock engined cars are running 108mph in 3800 pound cars on street tyres & after making more recent progress I believe that we can run 109-110mph,how does that compare to you guys?

Regards Glenn

Pro Stock John

iTrader: (34)

Why not invite some of the SD proponents over so we can argue with them.

SD tuning to me is old school, it's like tuning a an old school controller. You dyno and lock in all the parameters.

99% of our members can use MAF tuning and be very happy, do any of your SD tuners have any 10 second heads/cam cars? Any 9 second motor cars?

I know Ford guys who tune like that because they are using stuff like EPEC (sp?) and it's not because they want to. They end up changing the tunes depending on track weather and altitude.

And we have guys running 105-118mph with stock internals.

PSJ

Bink

Yeah - what he ^^^^PSJ said .

I'd like to follow the argument ...what's the address????
joel

VT2 EXEC LS1

Here ya go. It's long - 8 pages.

http://www.ls1.com.au/forum/showthre...threadid=18284

Bink

Thank You!!!
joel

v8 ute

One criticle part of doing a speed density tune is having a dyno that can hold the engine at certain load points.
Most of the dyno's in the USA don't do this (this is why the Aussies say, "The guys in US can't tune without MAF"), they are inertia dynos, where ours are eddy current.
Are the guys that are running the 9 and 10 second passes in the U.S. doing it with a 75mm MAF or an 85mm MAF?
Do they idle nice?

Bink

AND it is now Locked. FWIW.
joel

Brett SS

It's now unlocked again. Maybe some of you US guys could get in there and put forward some pro MAF arguements...

Slowhawk

iTrader: (12)

I've tuned my car both way's.SD ran a little better on the street but dyno'd the same.SD had a better throttle response for sure,but when the weather changed about 30 degree's the tune went off on me.Decided I liked ussing a MAF and tuned in the VE tables till it was just as responsive as SD.

AUSSIE TUNER

Thanks for your input Slowhawk,you answered the very question I was about to ask about the VE side of things.
Regards Glenn.

Bink

Slowhawk- did you modify VE cell by cell or did you scale in small (2-4%) percentages - I realize Large % changes foul up the fueling. Thanks!
joel

Slowhawk

iTrader: (12)

Mostly cell by cell Took forever to be happy with it.The sad part is I'll be changing my setup again,so start over

Bink

Thanks for the help. Sorry to here about the need for new tune....but new setup?? Elaborate a little?
joel

Slowhawk

iTrader: (12)

Testing some New Heads,the ones everybody is waiting for , then Cams to go with them and then Direct port on top of that.

vt2vx

I took some time to write this in a thread on ls1.com.au. so just copied it for here got bagged for making these points i might add.

from this tread http://www.ls1.com.au/forum/showthre...f&pagenumber=3

not been on here for a while.

Extract pasted:

Still I know Speed Density SD works well plenty of results to proove it does!

However I feel SD is more suited for the track, than it is for the road. This for someone that just wants to do a few mods and tune it, and leave it for a long time like it is, maybe some minor fiddles, the MAF tune would be better. If you want the most outa your car, race etc and are always changing things, retuning etc then SD is more suited.
Why, one point only really will spend some time and try to explain better than I usually do, think a bit, it hurts however. The purpose of any EFI system is to inject an amount of fuel into the engine. To do this, the PCM must know how much air is going into the motor at ANY given point.
What you should know is how much oxygen is in the combustion chamber at the time of ignition. The only way to tell how much fuel to inject in to mix with the available oxygen ( counting the molecules is hard) So you need to calculate the mass of air in the engine.
The amount of mass of air/gas in a given volume (the cylinder) depends on the temperature and pressure of the air. So SD setups measure the pressure in the intake manifold, and the current engine speed (which gives volume), from calculating these the pcm knows the mass of air in the combustion chamber. Speed density.SD is very fast, pretty accurate, and because it measures the intake charge in the intake manifold (close to the combustion chamber) it gives very good results.
But they have one problem, unless I’ve missing something else. The temperature and pressure of the intake charge in the cylinders wouldn’t be really the same as it is in the intake manifold. The air passes through the cylinder heads and past the valves first, and other factors can reduce or increase the amount of air that actually makes it into the cylinder. To allow for these differences, a speed/density PCM needs more info, the correction table called volumetric efficiency.
With volumetric efficiency (VE), you run the engine at each load point on a dyno, and manually adjusting the table until you get the correct air/fuel ratio as measured by an exhaust gas oxygen sensor. Then, after its is all perfectly tuned and producing nice power anytime after this you do anything else to the engine that changes breathing, you must recalculate all the VE points again.
This means as the engine ages, accumulates carbon deposits, cat converters clog up, etc etc etc, the VE of the engine is constantly changing, the perfect tune is constantly deteriorating. Emissions are also increasing overtime. It also means that if you do something to make a big change in VE - like change catbacks, extractors, intake systems, for example - that perfect SD engine tune will suffer. You need to go and reset the tune again

So holden like GM have used a different method of determining the mass air charge. Instead of the speed density systems, they use a sensor that measures air mass directly, a maf.
From the point of view of the factory, a maf is a great. As air mass is measured straight off the sensor, the maf compensates for wear, or ppl modifing the car to improve it (why you may need to reset the pcm to relearn). Since it has been mapped a given air mass vs RPM in the computer's tables, you can do what you like to the engine's VE and the computer can adjust for it. So you can make small changes and not stuff up your maf tune to much.

So it all depends on what you want to do with the car which tune to get. A maf tune is more forgiving, so could be said to be safer due to the point about VE and SD tunes.

MNC5

Twelve pages of almost nothing (yes I went through the whole thread) My advice is don't bother..lol. No before and after dyno's ect... just blah, blah,, Yanks can't tune ect... Seems like the land down under would be a good place to sell the

My guess is that unless your making huge HP & TQ #'s the only reason for any differences would be in the PCM tune its self. Not coming from removing the MAF. Just my .02 cents