Maxing out LS7 MAF, is there a frequency shifter?
Maxing out LS7 MAF, is there a frequency shifter? I am finding out that I'm maxing out the MAF frequency on my LS7 MAF in a 4 inch tube. I am maxing the frequency, NOT the max airflow. Given that it's already in a 4 inch tube, it seems like I need a frequency shifter or translator to shift the frequency back down within range. Remember this is on a 98 PCM, so I'm limited to something like 11250Hz or something like that. I remember the OOOG Harlan had a frequency shifter. What are my options other than going speed density?
I guess fundamentally, how do 1000hp cars run a MAF? Custom ECU with wider range? Different MAF sensor?
SPEED DENSITY NEED NOT APPLY.
Looks interesting but a shifter would only gain me a few KHz before I bottom out the low end.
http://www.gmtuners.com/tech/MAF_resistor_mod.htm
May try a frequency divider using a flip flop.
http://www.gmtuners.com/tech/MAF_resistor_mod.htm
May try a frequency divider using a flip flop.
TECH Addict
Joined: Dec 2004
Posts: 2,178
Likes: 627
From: Florida
How much repinning? I’ve converted two 97 vortec motors to 0411 ecus and it only takes a couple hours.
I can appreciate you being stubborn with maf and all that.
things that come to mind are the spacer I mentioned. A bigger intake tube. 5” shouldn’t be too hard to pull off. A ‘calibrated’ air leak post-maf.
a frequency divider sounds tricky to do diy. Back when I played motorcycle there were inline speedo recalibrators for when you change sprocket. Might be worth a look.
I can appreciate you being stubborn with maf and all that.
things that come to mind are the spacer I mentioned. A bigger intake tube. 5” shouldn’t be too hard to pull off. A ‘calibrated’ air leak post-maf.
a frequency divider sounds tricky to do diy. Back when I played motorcycle there were inline speedo recalibrators for when you change sprocket. Might be worth a look.
Trending Topics
100% I'm being stubborn. 🤣 A spacer is worth a try. I just don't see a 5 inch tube fitting without chopping my radiator support or get very creative. A simple D flip flop will act as a divide by 2 frequency divider. I can mill PCBs at work now so I could draw up something that goes in line with the MAF and halves the output. I think it's better than a shifter because it still keeps me above zero on the low end but will keep chopping the high end in half. So 11125 or whatever it is becomes half that and I pick up a bunch of head room. There are resolution concerns for cruising/part throttle but it may be the simplest option to test with. Are those Speedo recalibrations in terms of frequency or voltage?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
I would try a 3/4" spacer. If you have laminar flow, the center velocity is about 2x the average velocity in the tube and the velocity along the wall is zero. It forms a parabolic (not linear) curve that has been graphed. Assuming the MAF tip is in the center of a 4" tube, the 3/4" spacer should reduce the Hz signal by 25% and to get to 50% reduction it would need to be bout 1.4".
How much of an increase in the MAF headroom you looking for?
How much of an increase in the MAF headroom you looking for?
I would try a 3/4" spacer. If you have laminar flow, the center velocity is about 2x the average velocity in the tube and the velocity along the wall is zero. It forms a parabolic (not linear) curve that has been graphed. Assuming the MAF tip is in the center of a 4" tube, the 3/4" spacer should reduce the Hz signal by 25% and to get to 50% reduction it would need to be bout 1.4".
How much of an increase in the MAF headroom you looking for?
How much of an increase in the MAF headroom you looking for?
Edit...i apologize. I was dealing with an idiot on another forum and it carried over here. I'm already running a 4 inch (100mm) pipe with an LS7 MAF. We're talking about either a spacer in the existing pipe or going to a 4.5 or 5 inch pipe.
TECH Fanatic
Joined: Jan 2017
Posts: 1,758
Likes: 442
TECH Fanatic
Joined: Jan 2017
Posts: 1,758
Likes: 442
These guys make a maf housing up to 5" and can option in air straighteners. I think the 98 will have a hard time with these big mafs but you can of course experiment and try it out.
These guys make a maf housing up to 5" and can option in air straighteners. I think the 98 will have a hard time with these big mafs but you can of course experiment and try it out.
TECH Fanatic
Joined: Jan 2017
Posts: 1,758
Likes: 442
Dang that's a big housing! The ECU only knows frequency and airflow. I have a 50% scaled tune which gets around the airflow but you can't fake frequency. Boosted LS6. I really like the spacer idea that was mentioned. I may start there assuming I can either find or print one. Otherwise I'm going to build a frequency divider circuit. If that is a no go then maybe that 5 inch housing.
LOL boost is not the issue. I'm not going speed density on this car. I have a sticky on high HP MAF tuning for goodness sakes lol. Just going to add to my sticky showing how to get around the frequency limit.
- Bigger tube
- MAF translator (yes they still sell these things)
- Just go SD and be done with it and not worry anymore
You go speed density, not sure why you have an aversion to running it in SD as pretty much every higher power car does no matter if it's an OEM computer or standalone. Also the 99+ PCM swap is NOT hard, just a bit time consuming and you can run 3 bar without scaling like you have to do on a 98 PCM in SD.
- MAF translator (yes they still sell these things)
- Just go SD and be done with it and not worry anymore
You go speed density, not sure why you have an aversion to running it in SD as pretty much every higher power car does no matter if it's an OEM computer or standalone. Also the 99+ PCM swap is NOT hard, just a bit time consuming and you can run 3 bar without scaling like you have to do on a 98 PCM in SD.
- Bigger tube
- MAF translator (yes they still sell these things)
- Just go SD and be done with it and not worry anymore
You go speed density, not sure why you have an aversion to running it in SD as pretty much every higher power car does no matter if it's an OEM computer or standalone. Also the 99+ PCM swap is NOT hard, just a bit time consuming and you can run 3 bar without scaling like you have to do on a 98 PCM in SD.
- MAF translator (yes they still sell these things)
- Just go SD and be done with it and not worry anymore
You go speed density, not sure why you have an aversion to running it in SD as pretty much every higher power car does no matter if it's an OEM computer or standalone. Also the 99+ PCM swap is NOT hard, just a bit time consuming and you can run 3 bar without scaling like you have to do on a 98 PCM in SD.
Have you seen a maf translator that shifts the frequency? All the ones I've seen are for voltage and don't apply to our ECU. Harlan made one, but I dont see them anymore.
I have the GM maf in a 5" tube. I don't use it for anything other than actual airflow data.
But this was right around 11,000hz , fairly decent power, over 200mph in a standing half on the highway.
To give you the idea on range in a 5" duct