inkpot
SILVER Star
So without that limiting control factor, how much timing advance do you have when you are WOT at 4000 rpm? I think mind is pulled down into single digits, maybe around +2 -+4? I'll have to check on the way home tonite.
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The maf shouldn't see boost since it's before the compressor. If the maf was after then it would max out the maf voltage as you mention.
The supercharger does increase the intake air a great deal causing pinging. The ecu pulling the timing is it's reaction to stop the pinging. If a intercooler or meth injection is added to cool the intake air the ecu probably wouldn't reduce timing.
- Thread starter
- #24
Yeah. I hear you on the V8 swap. Ideally, that's what I'd like to do. Been reading here and looking around. An L92 or L76 with a 6L80E is the way I want to go(but I don't think the alt and ps pump setup on the L76 would work). I'm limited on how far I can go right now(planning on moving soon) but I'll slap a turbo on for 10-15k miles till I can get the LS lined up. Didn't get a chance to call CX today but it's looking like the turbo setup will be close to the $ of the S/C. Except the turbo will be I/Cd. Really considered building up an FE but $wise I'd be behind in the end.
I think the bottom end of my current engine is pretty solid. Cylinder walls looked really good when I swapped the head gasket.
I think the bottom end of my current engine is pretty solid. Cylinder walls looked really good when I swapped the head gasket.
In my opinion I would avoid the CX racing setup, especially if you want to go V8 later. You could recoup a large part of the TRD SC if you sell it later.
The MAF doesn't read boost, it reads air flow and then calculates volume in lbs. What I wrote is correct.
WOT in 2nd gear I've recorded 40* advance at 4800 rpms. I would have to go back and read data file to see what it is at 4000
- Thread starter
- #28
Appreciate the advice man. S/C is the way I want to go for now. I just wish there was an easier I/C setup to bolt on.
Has anyone here swapped a Gen V LS GDI engine in yet ? Cuz those fuel pumps would have to be stout to support the fuel pressure needed there.
No I meant the maf gets pre boost intake air, not boosted intake air. I didn't mean to indicate it's a vacuum or bar sensor.
Can you describe your work around to this issue? I'd be interested....
Actually the GDI engines are no longer LS's they are LT's and I highly doubt anyone has put one in an 80 yet. And the fuel system uses 2 pumps a normal low pressure pump in the tank and a second high pressure pump at the engine.
- Thread starter
- #32
Yup. You're right. Back around to LT now. Meant Gen V small block. lol. I think that'd be an awesome swap. GDI is more efficient and the tech behind it is pretty cool(like way different pistons and higher static compression ratios).
So what is your point?
Because the maf is before the compressor it shouldn't have any issue with the stock ecm pulling timing based on maf readings. If the maf is after the compressor then their may be a issue with the maf reaching max voltage and confusing the stock ecm.
inkpot
SILVER Star
No need to dig that out. Just now I did a freeway ramp WOT in 2nd gear and timing was at 36 degrees at 4500 rpm before I had to back out of throttle. My baseline timing is around 3-5 degrees advanced. So that is pretty close to the numbers you are seeing. I will have to play around with my rig and identifuly the conditions where I see the timing drop way low when at lower rpm WOT. I suppose I should just shift down and spinner up??!!
It is a sealed system. The amount past the SC'r is the same as the amount before the SC'r. You can't have a higher output without pulling more air past the MAF. I don't know anything about the SC'r and what MAF voltages it sees, but when you Turbo you can easily overwhelm the MAF, it is only part of why people have had issues with piggyback systems. The biggest challenge is the closed/open loop transition, the injector pulse width and the O2 sensors.
Huh that's interesting. I guess one positive to having it after the compressor would be more accurate intake temp readings. Sorry, I think in getting off topic of op. I'll shut up haha
Well yes and no. This is a very interesting subject and one that seems somewhat counterintuitive at first.
So the way a modern MAF measures how much air flow goes into the engine is that it heats an element red hot and then calculates how much voltage it needs to keep the wire that hot as air moves over it. The size of the MAF housing is known so there are some calculations using IAT to figure out the air has to move at a certain speed to require that voltage so calculating air volume is simply pi*radius^2*length of air column for unit time.
But when you compress that air it now acts differently.
For example take a coat hanger and get it red hot, now hold it up in a 40 degree f, 15mph breeze. How fast does it cool off? Take that same coat hanger get it red hot again but this time plunge it into a 40 degree f, river flowing 15mph. I bet it cools off much faster.
Much in the way the water is more dense than the air, the compressed air has a lot more ability to remove heat from the wire. The MAF is simply not calibrated for that so your engine has no idea how much air it's getting. In the "tuner" world this is called a suck through vs a blow through MAF.
If you have the ability via ECU to recalibrate the MAF either can be made to work, but as of yet no one has bothered to crack the 1FZ ECU.
So the way a modern MAF measures how much air flow goes into the engine is that it heats an element red hot and then calculates how much voltage it needs to keep the wire that hot as air moves over it. The size of the MAF housing is known so there are some calculations using IAT to figure out the air has to move at a certain speed to require that voltage so calculating air volume is simply pi*radius^2*length of air column for unit time.
But when you compress that air it now acts differently.
For example take a coat hanger and get it red hot, now hold it up in a 40 degree f, 15mph breeze. How fast does it cool off? Take that same coat hanger get it red hot again but this time plunge it into a 40 degree f, river flowing 15mph. I bet it cools off much faster.
Much in the way the water is more dense than the air, the compressed air has a lot more ability to remove heat from the wire. The MAF is simply not calibrated for that so your engine has no idea how much air it's getting. In the "tuner" world this is called a suck through vs a blow through MAF.
If you have the ability via ECU to recalibrate the MAF either can be made to work, but as of yet no one has bothered to crack the 1FZ ECU.
I suppose you could record live data both with the maf before the compressor and then record it with the maf after the compressor and see how much different the readings are. That would be interesting. So far I haven't had any issue running the toyota maf b4 the compressor up to a fair amount of boost so I haven't tried it otherwise.
had a local guy drop off his truck today. I supercharged it last year, it has 135k miles on it and the fueling system is competely stock. I took it out on the highway and data logged the RPM and associated timing. Below is a cut and paste from the file.
This was starting in 2nd and shifter dropped down into 2nd so as to avoid an upshift.
RPM .... Ign. Timing
648 ..... 4.5
646 ..... 4
654 ..... 4
654 ..... 4.5
654 ..... 4.5
664 ......1.5
618 ......7.5
605 ......6
608 ..... 5.5
871 ..... -1
2024 ... -5
1976 ... -5
2203 ... -1
2252 ... -1
2326 .... 1
2500 ....1.5
2637 .... 2
2815 .....3
3019 .....5
3320 .....6
3623 .....6.5
3771 .....10
3968 .....11.5
4273 .....11.5
4504 .....13.5
4708 .....14
4845 .....17.5
5040 .....22.5 <-Throttle lift
5144 .....25.5
5274 .....27.5
5165 .....40.5
5081 .....41
5040 .....41
4902 .....40.5
4735 .....27
4604 .....27
4295 .....27
3968 .....27
3576 .....27
3157 .....27.5
2615 .....26
2212 .....19
1765 .....13
1291 .....6
1073 .....4.5
775 .......4.5
558 .......7.5
622 .......7.5
630 .......7
618 .......6
618 .......4.5
608 .......4.5
608 .......4.5
610
You can see where I wrote throttle lift and the transition of the MAF signal dropping below that threshold which eliminates the timing pull and then the timing is now at the same point as a non supercharged engine.
This was starting in 2nd and shifter dropped down into 2nd so as to avoid an upshift.
RPM .... Ign. Timing
648 ..... 4.5
646 ..... 4
654 ..... 4
654 ..... 4.5
654 ..... 4.5
664 ......1.5
618 ......7.5
605 ......6
608 ..... 5.5
871 ..... -1
2024 ... -5
1976 ... -5
2203 ... -1
2252 ... -1
2326 .... 1
2500 ....1.5
2637 .... 2
2815 .....3
3019 .....5
3320 .....6
3623 .....6.5
3771 .....10
3968 .....11.5
4273 .....11.5
4504 .....13.5
4708 .....14
4845 .....17.5
5040 .....22.5 <-Throttle lift
5144 .....25.5
5274 .....27.5
5165 .....40.5
5081 .....41
5040 .....41
4902 .....40.5
4735 .....27
4604 .....27
4295 .....27
3968 .....27
3576 .....27
3157 .....27.5
2615 .....26
2212 .....19
1765 .....13
1291 .....6
1073 .....4.5
775 .......4.5
558 .......7.5
622 .......7.5
630 .......7
618 .......6
618 .......4.5
608 .......4.5
608 .......4.5
610
You can see where I wrote throttle lift and the transition of the MAF signal dropping below that threshold which eliminates the timing pull and then the timing is now at the same point as a non supercharged engine.
