Has anyone with a turbo relocated the MAFS to the post intercooler side of the system (i.e. right in front of the throttle body or there abouts). It seems the MAFS would get a better reading of exactly what is going into the engine at that point. However, I searched and didn't see anything on this, so there must be a reason why nobody (or not many people) have done it. Ideas?

I'm running a blow through setup that has the MAF mounted around 7" from the throttle body and works very well. It's nice to be able to read AITs and it offers good throttle response too.

I remember on some other cars people tried this but the MAF sensors were too fragile and broke in the compressed air stream. I don't know how fragile the RX-8 MAF is, but at under 14 pounds for more people, that isn't a boat load of boost. I think the situation I remember was around 25 pounds of boost people were running that MAFs broke.

I'm running a blow through setup that has the MAF mounted around 7" from the throttle body and works very well. It's nice to be able to read AITs and it offers good throttle response too.

I second GTAW. I have mine mounted in about the same spot as his and it works marvelously.

You'll just have to adjust the fuel maps slightly because the car will be a little rich. So far it has worked great... :)

Chris.....Esmeril

this is all good feedback. The next question is, has anyone done it with the GReddy kit. I've not seen a kit where there is a MAFS bung on the pipe right before the throttle body. How did you guys do it? Custom pipe and bung?

you would need a MAF bung and weld it to the pipe before the TB. Then you would need to remove the section of pipe where the MAF used to be and seal it up with a new solid piece of piping

Both the PTP and SFR kits use the blow through configuration. I plan to use this setup also.

this is all good feedback. The next question is, has anyone done it with the GReddy kit. I've not seen a kit where there is a MAFS bung on the pipe right before the throttle body. How did you guys do it? Custom pipe and bung?

I was discussing this with tdiddy the last time we ran into one another at a meet. If I go the custom turbo route some day, I might just save myself the hassle and use the MS CAI as it already incorporates the MAF on a 3" tube in the very location everyone is discussing. Really, though, this will be dependent on Cobb's recommendation after they release the Accessport.

^That would work, isn't the intake 3.5" tubing like the AEM? The MAF sensor is calibrated for 3.5", so you could use it as is. However, if you mounted it to the 3" pipe on the Greddy kit you would have to tune for it (like Chris has done) or recalibrate it, if Cobb does indeed make it an option. If anyone needs a MAF adapter, let me know, as I can make them for both 3 and 3.5" diameter tubing.
http://img165.imageshack.us/img165/1848/aluminummafadapterbj4.th.jpg (http://img165.imageshack.us/my.php?image=aluminummafadapterbj4.jpg)

^That would work, isn't the intake 3.5" tubing like the AEM? The MAF sensor is calibrated for 3.5", so you could use it as is. However, if you mounted it to the 3" pipe on the Greddy kit you would have to tune for it (like Chris has done) or recalibrate it, if Cobb does indeed make it an option. If anyone needs a MAF adapter, let me know, as I can make them for both 3 and 3.5" diameter tubing.

I'm sure you're correct and it is 3.5 not 3, I was just recalling off the top of my head.

Yes, the Mazdaspeed intake is 3.5". It could easily be modified to be used with the Pettit supercharger and using part of it could be possible for a custom turbo setup. I don't know if using the MAF mount piece would be easily done though. Notice in the pictures that the MAF mount piece has a slight bend in it. This could be a problem. Also, and probably more important, is the length of the MAF mount piece. It extends past the top cross member at the front of the engine bay. This could be a problem getting the piping from the intercooler to meet in with the MAF mounting piece. I'm sure it could be done but there might be easier ways.

Yes, the Mazdaspeed intake is 3.5". It could easily be modified to be used with the Pettit supercharger and using part of it could be possible for a custom turbo setup. I don't know if using the MAF mount piece would be easily done though. Notice in the pictures that the MAF mount piece has a slight bend in it. This could be a problem. Also, and probably more important, is the length of the MAF mount piece. It extends past the top cross member at the front of the engine bay. This could be a problem getting the piping from the intercooler to meet in with the MAF mounting piece. I'm sure it could be done but there might be easier ways.

Hmmm...what I'd had in mind from time to time was to run from the intercooler and attach to the MS/Maf mount like how Rotorocks did his rear mount turbo...probably relocate the battery to the trunk and place the intake filter there to lead down to the turbo. Though that location might be horrible for sucking in hot air from the engine bay, but no worse then the GReddy location.

One of his earlier pictures in the initial stages, but the idea is transparent:
http://www.rx8club.com/attachment.php?attachmentid=86995&d=1160961612

For that matter, I'd still like to figure out some way to Vmount an intercooler. I'm just not comfortable with a FMIC on a rotary.

For that matter, I'd still like to figure out some way to Vmount an intercooler. I'm just not comfortable with a FMIC on a rotary.


It takes a little work to fit in such a small space, but when it's all said and done, it's worth every penny.

We relocate the MAF right before the TB on our SFR turbo system.We made a custom MAF housing with screens in it as we found out that running this MAF without screens, right before the TB, lead to some erratic idle issues.

Hmmm...what I'd had in mind from time to time was to run from the intercooler and attach to the MS/Maf mount like how Rotorocks did his rear mount turbo...probably relocate the battery to the trunk and place the intake filter there to lead down to the turbo. Though that location might be horrible for sucking in hot air from the engine bay, but no worse then the GReddy location.

One of his earlier pictures in the initial stages, but the idea is transparent:
http://www.rx8club.com/attachment.php?attachmentid=86995&d=1160961612

For that matter, I'd still like to figure out some way to Vmount an intercooler. I'm just not comfortable with a FMIC on a rotary.

I see what your thinking now. You would be able to use everything except the "turn piece" that the filter connects to for that setup.

That's a good point, Tim. I bought a 304 stainless sample pack (part#92405T15) from McMaster.com (http://www.mcmaster.com/)and found the "30x30x.010" to work best for my setup.

We relocate the MAF right before the TB on our SFR turbo system.We made a custom MAF housing with screens in it as we found out that running this MAF without screens, right before the TB, lead to some erratic idle issues.

I experimented with the MAF in both positions and I found no benefit to having it post-compressor.
In theory, it would eliminate vented volume errors, but since I didn't have those to begin with, this benefit did not outweigh the consequences.
Erratic idle was persistent. Adding screens may have improved this, but I wasn't particularly sanguine about having all of that obstruction post compressor.

Having the IAT post compressor is a good idea, however.

I experimented with the MAF in both positions and I found no benefit to having it post-compressor.
In theory, it would eliminate vented volume errors, but since I didn't have those to begin with, this benefit did not outweigh the consequences.
Erratic idle was persistent. Adding screens may have improved this, but I wasn't particularly sanguine about having all of that obstruction post compressor.

Having the IAT post compressor is a good idea, however.

I'm guessing you have plans to move to the flash software, or at least experiment with it? Any thoughts on where you'll locate the MAF?

edit: seems many factory turbo cars, are locating the IAT pre turbo, never really got that logic myself as it would seem I'd want to favor reading the charge temps post intercooler...

Wouldn't vented volume errors best be handled with proper recirc?

Or through tuning.

You got a p.m. Fudgeboy.

You got an answer, stoopid beyotch!:lol2:

Thanks for all the input. The solution Synaptic3 is going with is using the blue MAFS mounting tube that comes with the Racing Beat kit. We are going to cut the pipe that comes up to the throttle body and insert the Racing Beat tube with silocone couplers there. Now clearly it would add quite a bit of complexity to put one of the screens in there before the MAFS. Also, would the airflow through the MAFS be as erratic post turbo/intercooler as it would directly post air filter like in an N/A application?

And please excuse my ignorance, but what is IAT?

The idle could be considerably more erratic since the air is "chopped" by the turbo.
The pipe diameter is also not a minor consideration. It is very difficult to "recalibrate" for the incorrect sizing of the charge pipe.

IAT = Intake Air Temperature sensor.

The idle could be considerably more erratic since the air is "chopped" by the turbo.
The pipe diameter is also not a minor consideration. It is very difficult to "recalibrate" for the incorrect sizing of the charge pipe.

IAT = Intake Air Temperature sensor.

Thanks MM. Would you suggest we go down a route of trying to get a screen in that racing beat tube before the MAFS? Thats a big restriction (as you mentioned) and I'm also worried about the screen coming loose in there.

The piping diameter for the racing beat MAFS pipe is 3.5" which makes it perfect for this, except the screen issue. I'll have to look into the racing beat setup to see how the screen is in there again.

Anyone else running this?

Thanks MM. Would you suggest we go down a route of trying to get a screen in that racing beat tube before the MAFS? Thats a big restriction (as you mentioned) and I'm also worried about the screen coming loose in there.

Anyone else running this?

as MM put it - "chopper" air, probably would not be to big of an issue past intercooler. The air will have plenty of time to get "back together", however you may probably want to keep it away from the BOV somewhere.
Get a thiker mesh with larger cells, if you worry about it breaking.

as MM put it - "chopper" air, probably would not be to big of an issue past intercooler. The air will have plenty of time to get "back together", however you may probably want to keep it away from the BOV somewhere.
Get a thiker mesh with larger cells, if you worry about it breaking.

you mean keep the MAFS away from the BOV correct?

Unless someone can show significant advantage over a properly installed and tuned setup with the MAF before the turbo, this doesn't sound like the relocation effort is worthwhile.

And besides air loss from a non-recirculated BOV, the MAF should read the same either way.

I'd rather have screens on the non compressed air stream too.

And you probably remember, Tim, that the MAF/screen issue is about 3 years old now. It is always suggested to use at least one screen in front of the MAF sensor. One thing I was able to do was use a Blitz SUS filter and the MAF didn't seem to mind having no screen in front.


Nobody mentioned it in this thread so I thought I would.:lol2:

you mean keep the MAFS away from the BOV correct?

Yes.
Opening and closing BOV will cause a lot of turbulence, which will get you MAF sensor confused real quick.

This makes no difference when using Int-X/Microtech though, as with Microtech you only make use off the intake temperature, which in most kind of useless.
GTAW can you PM me on the details for that MAF flange?
I don't have it inserted anywhere. My MAF is just sitting in the engine bay, telling me how hot it is in there, but I would like to install it just for the cosmetic (complete look) purposes.

Unless someone can show significant advantage over a properly installed and tuned setup with the MAF before the turbo, this doesn't sound like the relocation effort is worthwhile.

And besides air loss from a non-recirculated BOV, the MAF should read the same either way.

I'd rather have screens on the non compressed air stream too.

Well, i guess once you tune it maybe it won't matter? The thought is that by putting the MAFS in front the the TB, it will read the air that is going into the engine whereas in its current location that isnt necessarily the case.

The thought is that by putting the MAFS in front the the TB, it will read the air that is going into the engine whereas in its current location that isnt necessarily the case.


Exactly.You will get much more accuate air metering as you are measuring the air after it gets compressed, goes though the intercooler and piping,etc........The chances of sucking in unmetered air and potentially running lean is greatly minimized.

Exactly.You will get much more accuate air metering as you are measuring the air after it gets compressed, goes though the intercooler and piping,etc........The chances of sucking in unmetered air and potentially running lean is greatly minimized.

Tim, another question. Do you use 3.5" piping throughout the system (intake to turbo to intertooler to MAFS to TB)? wondering about the flow implications of not using uniform piping diameter throughout the whole sustem.

For measurement purposes, it only matters right at the MAF.

Even for the INTX it matters. It gets the AIT from the MAF. And I would much rather have the AIT of the compressed air instead of the pre-compressed air.

Has anybody pegged the MAF sensor yet? I remember someone saying it's good for 500 hp... Now that I'm getting closer to a good tune, I'm starting to wonder if it's good for even 400.

Tim, another question. Do you use 3.5" piping throughout the system (intake to turbo to intertooler to MAFS to TB)? wondering about the flow implications of not using uniform piping diameter throughout the whole sustem.

It starts off at 2.5' then transitions to 3" and the MAF sensor is 3".


Tim

Has anybody pegged the MAF sensor yet? I remember someone saying it's good for 500 hp... Now that I'm getting closer to a good tune, I'm starting to wonder if it's good for even 400.

Kane is working on that right now.

It has an operating range of 0 to 5 volts.
It idles at 1.16 volts or so and at the torque peak, about 4.5 volts is seen on a 330 HP run, so the earlier estimates are probably a bit optimistic.

In a few more days, I should be able to get a good table of MAF voltage to lb/min of air.

U guys need it?

Kane is working on that right now.

It has an operating range of 0 to 5 volts.
It idles at 1.16 volts or so and at the torque peak, about 4.5 volts is seen on a 330 HP run, so the earlier estimates are probably a bit optimistic.

I was under the impression that our MAF is the same model that is used in the STi...

It is.

In a few more days, I should be able to get a good table of MAF voltage to lb/min of air.

U guys need it?

That would be cool to have in your software.

I'll hit it up this weekend. It will be +/- the accuracy of Jeff A/F gauge.

I'll hit it up this weekend. It will be +/- the accuracy of Jeff A/F gauge.

I'm using a well-calibrated LM-1, which has been acknowledged in many reviews as the most accurate Bosch-based A/F meter available.
You have to spring for a Horriba (at $2k) to get something "better" and its "better-ness" is debatable.

HAHA, I figured you would jump on that. I trusted ya', and I have heard good tings about the LM1.

Here is the graph and excel file.

Remember these are averages over a few hundred thousand points.

http://www.rx8club.com/attachment.php?attachmentid=105592&stc=1&d=1186764776

The high end for Jeff was 4.47 at 38 lb/min of air. So you should def get to at least 45-50 lb/min I would think.

I think the variation would be from either BOV or spooling up, or both. But am not really sure.

Thanks Kane, the graph gives us a good idea on where we stand. It looks like the MAF may be good for about 50 lbs/min.

Right now, at 5-6lbs of boost, I'm hitting between 4.45 and 4.57v at around 8000-8500 rpms with a 60-1 turbo. The plan is to run 9-10 lbs up to redline once I'm happy with the tune at the lower boost levels and slowly progress from there, until either the MAF is maxed or the ignition gives up the ghost.

I've been using Innovate's LC-1 and digital gauge package for about two years. The bung is welded about 3' away from the downpipe and the unit is stilling going strong. I recalibrate it every couple of months just to be on the safe side and overall, couldn't be happier with it.

PS. I added the MAF Decoder to my software. You can see your MAF to airflow and you can recalibrate the MAF as well if you need to (piping).

http://www.rx8club.com/attachment.php?attachmentid=106131&stc=1&d=1187473453

Updated MAF

The only issue I see with your premise Charles, is the BOV... I do not know what a vented BOV does to the MAF when it goes. At 29 lbs/min (FI 11.5 AFR), you are somewhere around....260 HP. So 35 lb/min at 12:1 would be well over 300... can't find proof just yet.

Your assumptions are correct - if at 180 lb/hours of fuel (12.1 AFR), that is 87% more than stock fuel maximum... so given enough air to support it, you could theoretically say that you can make 87% more power than the stock fuel system can handle before the MAF gives out (which is +/- 300 hp?)... semi-educated guess... 561 HP if you were NA (in a perfect world). That is just the MAF sensor, not the engine. And FI, you drop down.

I think I did something wrong up above... but I don't have my math book in front of me. Gimmie a sec...

Approx Horsepower =([MFR-FI]*60)/(AFR*0.6) Yeah I was too high.

Forgot the BFSC... so 38 lb min is 315 hp.... if our engine BFSC is 60%

Wait the higher the BSFC goes up, the lower the HP drops....

Now I am confused.... BSFC refers to loss of engine eff. due to inertial resistance/ heat lost to engine on exhaust/ heat absorbed on intake right?

If the MAF is mounted pre-boost why would the numbers skew downward in term of h.p.?

Loss of power due to being over rich.

376 HP with a BSFC of .5

Yes Charles,

I have been f-ing around and I found BSFC from .35 to .44 on rotaries (via the web, so not real reliable).

376 HP


http://www.xsltblog.com/archives/24805BP~The-Simpsons-Mr-Burns-Excellent.jpg


S

Have fun man!!!

Yes, so lower BSFC mean more HP. At .44 BSFC we have 422 HP!!!

BTW, Kane, I sense our prior conversation re: airflow vs. fuelflow is becoming clearer to me. Not to say either is wrong just that I see further applications of each perspective.

LOL, yes one day we will have it out!!!!!

I know, I was just trying to be funny.

BSFC = fuel lbs/hr.
On a piston motor, its about .5 and on a rotary motor it is about .6 or so.

No. BSFC and VE are independent.
There is no good median VE, especially on an engine with a wide RPM range and power band.
The Renesis goes from 35% to over 100% in its OE form, so its hard to say it is an average or 67%!
BSFC is a fairly constant number since it only applies at WOT and peak torque.

You guys want me to do a VE curve as well?

This is great stuff here. I'm actually now running into an issue with the MAFS sensor on my turbo install. The ECU is throwing a CEL which is "high voltage MAFS" code. Apparently the MAFS is reporting higher than the 5 volts its supposed to. Is it possible for this MAFS to be overrun at 4-5 psi or lower? Or is it more plausable the MAFS is broken. We had to clean it prior to this because this because the car would not even run. After cleaning it we get this code. Any ideas?

Thanks Charles. I don't have the specific code number but my installer pulled it with his scantool and it read as high MAFS voltage. The car also goes into limp mode after a certain RPM (around 4k i believe).

I did some research and most say this MAFS should be good up to around 500 hp, but I also found there was a recall/TSB for the MAFS in 04 rx-8s for premature failure.

Replace it...they're cheap....and see if it fixes the problem ;)

The MAF should never deliver more than 5v.