Altering the MAF on a 1992 SC400....
- Thread starter jibbby
- Start date
The 1UZFE EGR Delete Kit is available for sale here.
No, seriously the Karman MAF airflow passage just looks so restrictive as shown in the pictures above, and it appears there are minor intake gains to be made either with the a MAF mod/tuning and or larger Throttle body. I would think even on a N/A motor with a piggy ECU and Nos. I want this engine to breathe and I just think the possibility of a bigger intake should do something positive, but maybe not.......A future FI is likely but maybe not on this motor.... Just seeking out options and the full truth behind this stock intake setup and what can be done..... I am about to give up with this but wanted to take one last stab at it...
Nothing wrong with it all and I probably shouldn't be concerned about it, but I like to experiment and mess with stuff, tinker and ultimately break things...MightyAl said:
No, seriously the Karman MAF airflow passage just looks so restrictive as shown in the pictures above, and it appears there are minor intake gains to be made either with the a MAF mod/tuning and or larger Throttle body. I would think even on a N/A motor with a piggy ECU and Nos. I want this engine to breathe and I just think the possibility of a bigger intake should do something positive, but maybe not.......A future FI is likely but maybe not on this motor.... Just seeking out options and the full truth behind this stock intake setup and what can be done..... I am about to give up with this but wanted to take one last stab at it...
I have tuned several high performance engines with MAP sensor based EFI. It ends up working very well and can make huge power quite well. The biggest problems I ran into was at light loads, especially on a Honda with big cams. Idle was near impossible to tune nice with just the MAP sensor for a signal. The motor only pulled 12 inches of vac at 900 rpm, but it shot to 18 inches of vac by 1500 rpm. This suggests it needs less fuel, but it really needs more. For a test, I added a small ford hot wire MAF sensor and looked at its output. I used it to help me tune the V.E. table values for the MAP sensor. Had I just tuned it for the MAF, it would have been simple, but the sensor was way too small as it was from a 3.0L Taurus that topped out at just 160 hp and this little 1.6L made close to 300 hp at just 12 psi of boost. Once I got in the ball park using the flow numbers from the MAF sensor, I completed the tune with a wide band O2 sensor system. After seeing how nice the data from a MAF worked, I actually picked up a KV AFM from a 7MGTE to try and use on my turboed 22RE 2.4L Never finished that idea, but it looked very promissing.
Most MAF's and AFM's only measure part of the air flowing through them. The mesh (or screens) on the sensors ensure that the ratio of flow being measured to the bypassed flow holds constant as the total flow changes. Most Ford units have the same electronics, but the housings have bigger bypassing passages on the higher power motors. My 3.0 Taurus meter was identical to the 5.0L Mustang meter except for the size of the un measured hole. I believe Toyota did the same thing with the 7MGTE and the 1UZFE units. The passages next to the meter bar are bigger on the 1UZ. The ECU is programmed with the ratio of signal to CFM of air. Change the amount of bypass air and the mixture will be wrong. The same signal off of a 1UZFE meter means more air than that from the 7MGTE meter. Using the bigger injectors fakes out the ECU to provide the proper mixture again. I used a strong shop vac to compare the signals of several AFM's. If you do anything to get more air through the AFM, you need to make sure it provides the same signal frequency for a given amount of air flow, or you adjust the injector size for the proper air flow. Adjusting the injectors (and/or fuel pressure) can get the mixture back over a fair range, but also keep in mind the spark timing will also change with this type of mod. Using a bigger air meter that gives a smaller reading (and using bigger injectors to compensate) may result in perfect mixture, but the ECU "thinks" the engine is under lighter load so it runs more ignition advance. This could result in detonation.
Personally, I am leaving the AFM alone until I am certain I exceed it's limit. I will monitor the vacuum drawn between the throttle and the AFM (and between the filter and AFM). If it is a small amount of vac, the AFM is not a problem. A guy who put a 90 mm throttle on a Honda was annoyed when he didn't get any improvement in acceleration. It turned out he was not pulling any vacuum behind the stock throttle, so going with a bigger hole made no change. All it did do was make 1.2 throttle pull as hard as wide open before, and 1/2 to WOT made no change at all. It just made it near impossible to drive smoothly as it would rev hard from a tiny touch on the pedal.
Once you do go to boost though, the MAP sensor is king for several reasons. A HUGE AFM that cam meter that much flow will not have near as good of resolution as the MAP sensor. Blow off valves on MAF (AFM) systems need to be connected back into the system after the AFM or the mixture goes out the window when it opens. Any leak after a flow meter will mess with mixture, MAP sensors don't car how the air gets into the manifold, it fuels the same whether it is a leak, the brake booster, or even the A/C control head idle up VSV. The bad part about MAP is that any change in the flow rate of the engine requires a re tune. By chnaging the cam in my 2.4 turbo I had to decrease the V.E. table values from idle to 2500 rpm by almost 10%, then increase them nearly 20% from 4000 rpm on up 5500. At 6500 or so it was about back even as the head could no longer flow up there. The ported head required the 5000 to 7000 rpm ranmge to be increased another 10%. All this for the same MAP sensor readings. I actually had to drop max boost from 15 to 13 psi because the injectors could no longer keep up. A MAF system should just see the new found flow and inject the extra fuel (within it's flow range)
Gary M.
Most MAF's and AFM's only measure part of the air flowing through them. The mesh (or screens) on the sensors ensure that the ratio of flow being measured to the bypassed flow holds constant as the total flow changes. Most Ford units have the same electronics, but the housings have bigger bypassing passages on the higher power motors. My 3.0 Taurus meter was identical to the 5.0L Mustang meter except for the size of the un measured hole. I believe Toyota did the same thing with the 7MGTE and the 1UZFE units. The passages next to the meter bar are bigger on the 1UZ. The ECU is programmed with the ratio of signal to CFM of air. Change the amount of bypass air and the mixture will be wrong. The same signal off of a 1UZFE meter means more air than that from the 7MGTE meter. Using the bigger injectors fakes out the ECU to provide the proper mixture again. I used a strong shop vac to compare the signals of several AFM's. If you do anything to get more air through the AFM, you need to make sure it provides the same signal frequency for a given amount of air flow, or you adjust the injector size for the proper air flow. Adjusting the injectors (and/or fuel pressure) can get the mixture back over a fair range, but also keep in mind the spark timing will also change with this type of mod. Using a bigger air meter that gives a smaller reading (and using bigger injectors to compensate) may result in perfect mixture, but the ECU "thinks" the engine is under lighter load so it runs more ignition advance. This could result in detonation.
Personally, I am leaving the AFM alone until I am certain I exceed it's limit. I will monitor the vacuum drawn between the throttle and the AFM (and between the filter and AFM). If it is a small amount of vac, the AFM is not a problem. A guy who put a 90 mm throttle on a Honda was annoyed when he didn't get any improvement in acceleration. It turned out he was not pulling any vacuum behind the stock throttle, so going with a bigger hole made no change. All it did do was make 1.2 throttle pull as hard as wide open before, and 1/2 to WOT made no change at all. It just made it near impossible to drive smoothly as it would rev hard from a tiny touch on the pedal.
Once you do go to boost though, the MAP sensor is king for several reasons. A HUGE AFM that cam meter that much flow will not have near as good of resolution as the MAP sensor. Blow off valves on MAF (AFM) systems need to be connected back into the system after the AFM or the mixture goes out the window when it opens. Any leak after a flow meter will mess with mixture, MAP sensors don't car how the air gets into the manifold, it fuels the same whether it is a leak, the brake booster, or even the A/C control head idle up VSV. The bad part about MAP is that any change in the flow rate of the engine requires a re tune. By chnaging the cam in my 2.4 turbo I had to decrease the V.E. table values from idle to 2500 rpm by almost 10%, then increase them nearly 20% from 4000 rpm on up 5500. At 6500 or so it was about back even as the head could no longer flow up there. The ported head required the 5000 to 7000 rpm ranmge to be increased another 10%. All this for the same MAP sensor readings. I actually had to drop max boost from 15 to 13 psi because the injectors could no longer keep up. A MAF system should just see the new found flow and inject the extra fuel (within it's flow range)
Gary M.
Wow, good post...Although times like this I sure miss my old Chevy's. All I would need is timing light, carb screw drivers for adjusting, hand slight turn or twist of the distributor right or left and I could tune those small blocks to perfection...Oh those good old days.......
Yeah that is true, but you have ECU computers that are rediculous, dual over head cams, fuel injection, MAF. etc...just a hole new ball game when comparing these engines to the engines of 25-30 years ago... I am not saying today engine is worse just more to learn and deal with....I just enjoyed the simplicity of those earlier motors....
Bottom line is if you were a professional mechanic of 25 years ago and you take a 25 year vacation you had better find a new line of work because you will be lost with todays engines.....
Bottom line is if you were a professional mechanic of 25 years ago and you take a 25 year vacation you had better find a new line of work because you will be lost with todays engines.....
25 years ago would be 1981. Wow, some of the cars on the road back then were pure junk. The stupid things detroit did to try and pass the tightening emissions requirements made working on some of those cars a nightmate. My fathers 79 Lincoln Town car had a 5.0 V8 with a 4 barrel carb rated at 155 hp. It probably had a mile of vacuum hoses and couldn't do 0-60 in 12 seconds. All while getting about 14 mpg. My sister also picked up a 1982 (or was that 84) Mustange GT, but she got it with an auto trans so it had the 5.SLOW with a throttle body injection system making all of 140 hp. What a slug. At least our 1980 Chevy Suburban had a 5.7 (350) with a big 4 barrel and dual exhausts with a TH400 trans and 4.11 gears. It still sucked gas like hell but it ran to 60 faster than most Camaros of the time. Too bad the motor was out of breath by 70 mph. It felt like it was revving 5,000 rpm just to do 65. No tach, so I can't confirm, but with no overdrive and that 4.11 gear....
I sure think a MAF sensor and ECU is a whole like nicer than the Bosch CSI mechanical injection from back then. I think you needed a lab coat to work on those things.
Gary M.
I sure think a MAF sensor and ECU is a whole like nicer than the Bosch CSI mechanical injection from back then. I think you needed a lab coat to work on those things.
Gary M.
Yeah Gary those 80's cars were not all that impressive....I remember in the 80's when (TPI) tune port injection came out and that the big thing. To me was the turning point in my opinoin (fuel injection) in the auto industry ..
However, I was just saying those 2 and 4 barrel carbs could give you trouble at times but they were either easy to rebuild or adjust if needed...Today you need software and computer, etc...to tune your cars...Days have changed that is all I am saying since then..really changed.....
However, I was just saying those 2 and 4 barrel carbs could give you trouble at times but they were either easy to rebuild or adjust if needed...Today you need software and computer, etc...to tune your cars...Days have changed that is all I am saying since then..really changed.....
