Robb235's Front Mount Turbo Build

[Robb235]

OK, I have read this a few times, trying to follow the logic. I like to believe this stuff is simple logic, but it does require understanding of the principles involved and maybe I'm not fully dialed in. Let me be clear though, this is NOT a criticism, it is an attempt to understand. Because its not making sense, to me.

Let's start with the following statement.

"For example, let's say you increase the MAF tube by 30%. Now the ECU thinks the engine is inhaling 30% less air, and injects 30% less fuel than it normally would. Now add 30% larger injectors, and it brings you back to where you need to be."

Are you saying that because the OEM MAF is calculating the air flow based on a specific tube diameter that it won't detect the additional air flow? Will it just assume the airflow is what it would be if the tube diameter was unchanged? I just can't get my head around that. Because the air flow isn't a static thing, it is dynamic and I'm sure there will be some changes, I just don't know what that would be. I'd want more explanation before I made changes.

I think you're way overthinking this. Our trucks use a "hot wire MAF", where there is a heated wire in the intake stream. That wire is heated, and the more air that flows over the wire (i.e. the more you open the throttle body), the more that wire is going to cool down. The ECU measures this, and calculates how much air is going in. But if you change the diameter of the MAF tube and make that diameter larger, then the air is not going to move as quickly past the heated element, not cooling it down as much, making the ECU perceive that less air is flowing.

The opposite is true if you make the MAF housing diameter smaller. Now, the air is going to be rushing past the heated element much faster, cooling it much quicker, and causing the ECU to perceive this as more air entering the motor.

Second thing is the math here.

"In my case, the 315cc injectors are 31% larger than stock. To change the MAF tube from the stock 2.75" to 3" would be a change of 19%. The 31% increase from the injectors, minus the 19% increase MAF diameter still means that the computer would run 12% richer than expected, however, I feel that the ECU could adjust for that via the Long Term Fuel Trims."

Using the formula Pi X r2.

Radius of 3 is 1.5
1.5 x 1.5 = 2.25
2.25 x 3.14 rounds up to 7.07

Radius of 2.75 is 1.375
1.375 x 1.375 =1.89
1.89 x 3.14 rounds up to 5.94

The difference is 1.13

1.13 divided by 7.07 is 0.159, or 16%

I know I'm splitting hairs, but if we are going to be scientific about your approach, lets do it right. Now your airflow, assuming we are correct, is only 1/2 what the fuel flow is increased.

Actually you're partially correct.

What you proved is that statement of "a 2.75in pipe has 16% less area than a 3in pipe", which is true.

However, what I proved is the statement "a 3in pipe has an area 19% larger than that of a 2.75 dia. pipe"

Here's why:

As you have already proved...
2.75" pipe = 5.94 square inch area
3" pipe = 7.07 square inch area

7.07 / 5.94 = 1.19 (basically says that 7.07 is 1.19 times larger than 5.94, or in other words, is 19% larger).

 

[IBallEngineer]

I believe his reasoning is this:

Fundamentally, the engine is going to draw as much air as it is being asked to draw, and capable of drawing. When you say "higher RPM please", you're telling the engine to draw more air and expect the ECU to mix in the right amount of fuel.

The MAF detects airflow (and assumes a bore area of pi * 2.75^2= 23.76 square inches) and the ECU uses that to determine how much fuel to send (and assumes stock injectors.)

When he increases the injector size by 31%, he's increasing the fuel that the ECU injects (in response to the airflow it assumes is coming through a stock intake) by 31%.

That throws the AF ratio off, so he increases the diameter of the MAF bore to pi * 3^2= 28.27, which is 19% larger. But the MAF doesn't know the bore is larger, so when it sees air going by, it doesn't know 19% more is passing through than usual. So it tells the ECU "you're getting 1 unit of air" when it's really getting 1.19 units, and the ECU says "I'm injecting 1 unit of fuel" when really it's injecting 1.31. The ECU will then detect that it's burning a bit rich, assume something is odd (like a squirrel nest in the air filter box), and correct for it via fuel trim.

It's pretty clever. I have no idea if it's going to work, but I'm eagerly watching this thread to see. It's a pleasingly simple solution.

OK but the formula for the area of a circle is Pi x the RADIUS SQUARED. Not the diameter.

 

[0xfded]

What I want to know is how the rate of airflow is effected by pressuring the system to 7 psi? In theory, wouldn't it reduce the airflow by comparison to the naturally aspirated system?

That's a great question, I'd like to know too. I don't think our MAF sensor wouldn't be able to detect a static increase in pressure, only a change in flow rate.

Going to learn a bunch from this thread. opcorn:

 

[Robb235]

I believe his reasoning is this:

Fundamentally, the engine is going to draw as much air as it is being asked to draw, and capable of drawing. When you say "higher RPM please", you're telling the engine to draw more air and expect the ECU to mix in the right amount of fuel.

The MAF detects airflow (and assumes a bore area of pi * 2.75^2= 23.76 square inches) and the ECU uses that to determine how much fuel to send (and assumes stock injectors.)

When he increases the injector size by 31%, he's increasing the fuel that the ECU injects (in response to the airflow it assumes is coming through a stock intake) by 31%.

That throws the AF ratio off, so he increases the diameter of the MAF bore to pi * 3^2= 28.27, which is 19% larger. But the MAF doesn't know the bore is larger, so when it sees air going by, it doesn't know 19% more is passing through than usual. So it tells the ECU "you're getting 1 unit of air" when it's really getting 1.19 units, and the ECU says "I'm injecting 1 unit of fuel" when really it's injecting 1.31. The ECU will then detect that it's burning a bit rich, assume something is odd (like a squirrel nest in the air filter box), and correct for it via fuel trim.

It's pretty clever. I have no idea if it's going to work, but I'm eagerly watching this thread to see. It's a pleasingly simple solution.

Yes! This is exactly what I was trying to explain. I think you did it in a much more concise and easier to understand way than what I did.

Tricking the maf is not a good idea. If you go to far the ecu could still think its in closed loop and at WOT you will be on a very high timing curve which could cause lots of detonation. This is why piggy back EMS suck. People will run e85 to try and combat that super high timing curve.

And that is the only real downfall I see to this "hack" that I'm talking about. With the ECU thinking that less air is entering the motor, it's going to assume a lower calculated load value, and advance timing. But my question is, "how much"? Is the increase from a 2.75" MAF housing to a 3" MAF housing enough to cause the ECU to advance timing waaaaaay too much? Or will it make no real world difference? That's more what I was wanting to discuss, because I have no idea how much "weight" the ECU places on the perceived amount of air entering the motor versus the timing curve.

 

[0xfded]

OK but the formula for the area of a circle is Pi x the RADIUS SQUARED. Not the diameter.

Whoops, of course. Second time you've caught that mistake...

 

[Robb235]

OK but the formula for the area of a circle is Pi x the RADIUS SQUARED. Not the diameter.

You're right, but it's the ratio between the two that we care about, not the empirical numbers. Either way, you still come up with 19%.

 

[Robb235]

That's a great question, I'd like to know too. I don't think our MAF sensor wouldn't be able to detect a static increase in pressure, only a change in flow rate.

Going to learn a bunch from this thread. opcorn:

The air is compressed, therefore more air molecules are hitting that heated element, so it doesn't detect the differences in air pressure, but does detect the difference in the mass of air that is moving through the intake. At least, that's the way I understand it.

 

[IBallEngineer]

Here's why:

As you have already proved...
2.75" pipe = 5.94 square inch area
3" pipe = 7.07 square inch area

7.07 / 5.94 = 1.19 (basically says that 7.07 is 1.19 times larger than 5.94, or in other words, is 19% larger).

So it's a 19% markup, as opposed to a 16% discount.

I stand corrected.

 

[1985taylor1925]

Im learning a lot in this thread. Some new info for me.

And that is the only real downfall I see to this "hack" that I'm talking about. With the ECU thinking that less air is entering the motor, it's going to assume a lower calculated load value, and advance timing. But my question is, "how much"? Is the increase from a 2.75" MAF housing to a 3" MAF housing enough to cause the ECU to advance timing waaaaaay too much? Or will it make no real world difference? That's more what I was wanting to discuss, because I have no idea how much "weight" the ECU places on the perceived amount of air entering the motor versus the timing curve.

So to this issue . . . if you didn't want to do a "hack" job, how would you go about it to be certain that timing would be correct, or could be tuned. Would you use a different MAF altogether? Or can something be used for tuning the ecu, like a URD 7th injector? Again, much of this is new to me

 

[Cree]

So to this issue . . . if you didn't want to do a "hack" job, how would you go about it to be certain that timing would be correct, or could be tuned. Would you use a different MAF altogether? Or can something be used for tuning the ecu, like a URD 7th injector? Again, much of this is new to me

MAF doesn't determine timing. The only way to truly be certain would be to change the timing tables in the tune, which apparently you can't do with these ECU's.

My understanding is the 7th injector just adds fuel to combat detonation. He's already accomplishing the same thing with the larger injectors.

What's the voltage range on a Stock maf? And how are these changes going to affect it? Or are you just hoping to trick it enough to run in a constant rich state? 12% is quite a bit for the comp to pull. Most of the EFI systems I'm familiar with can work with between 6 and 10%.

 

[Robb235]

MAF doesn't determine timing. The only way to truly be certain would be to change the timing tables in the tune, which apparently you can't do with these ECU's.

My understanding is the 7th injector just adds fuel to combat detonation. He's already accomplishing the same thing with the larger injectors.

What's the voltage range on a Stock maf? And how are these changes going to affect it? Or are you just hoping to trick it enough to run in a constant rich state? 12% is quite a bit for the comp to pull. Most of the EFI systems I'm familiar with can work with between 6 and 10%.

The larger injectors are needed because whether supercharged or turbo'd, you will quickly max out what the stock 240cc injectors can flow, especially higher up in the RPM range. Same idea with the 7th injector kit. In order to run richer than 14.7 in closed loop, you'd have to use a piggy back of some kind that fools the O2 sensor, which you can get from URD. Eventually I'll look into doing something like that.

As far as saying that the MAF doesn't determine timing, I don't know that I agree with that. I believe that it indirectly does. I could be wrong, but I'm pretty sure that timing advance is heavily influenced by the calculated load on the engine. Calculated load is a value you can measure with a hand held scan tool (like a Scangauge2 or iPhone or Android app), and is calculated by TPS, MAF, RPMs, IATs, etc.. If the ECU is "fooled" into thinking it's taking in less air than it actually is, then it would report a lower Calculated Load value, and therefore advance timing. That's my take on it anyways. If you're able to disprove my understanding of this, feel free to, I love discussions like this.

Also, I'm pretty sure the ECU can go as far as +20% or -20% on the Long Term Fuel Trims. Any more than that, and the ECU will pop up with a "system too rich" or "system too lean" CEL.

 

[Cree]

The larger injectors are needed because whether supercharged or turbo'd, you will quickly max out what the stock 240cc injectors can flow, especially higher up in the RPM range. Same idea with the 7th injector kit. In order to run richer than 14.7 in closed loop, you'd have to use a piggy back of some kind that fools the O2 sensor, which you can get from URD. Eventually I'll look into doing something like that.

We're saying the same thing bro.

As far as saying that the MAF doesn't determine timing, I don't know that I agree with that. I believe that it indirectly does. I could be wrong, but I'm pretty sure that timing advance is heavily influenced by the calculated load on the engine. Calculated load is a value you can measure with a hand held scan tool (like a Scangauge2 or iPhone or Android app), and is calculated by TPS, MAF, RPMs, IATs, etc.. If the ECU is "fooled" into thinking it's taking in less air than it actually is, then it would report a lower Calculated Load value, and therefore advance timing. That's my take on it anyways. If you're able to disprove my understanding of this, feel free to, I love discussions like this.

No, you're right. It does play it's part. I was simply replying to the guy I quoted, as it seemed he thought that the MAF somehow directly dictated the timing curve.

Also, I'm pretty sure the ECU can go as far as +20% or -20% on the Long Term Fuel Trims. Any more than that, and the ECU will pop up with a "system too rich" or "system too lean" CEL.

Well, since I wasn't sure and it didn't sound like you were positive either, here's what I turned up.....

4x4Wire - Tech: Understanding OBDII Engine Systems and Fuel Mixture Control

It sounds like you can do 35% before getting a MIL. So you might be onto something with tricking the MAF as far as fuel trims go. However, it looks like you have a fairly small range of voltage to play with before tripping a light, which was part of my original question.


And for context, so you don't think I'm just some dumb guy that doesn't post much and may not have an idea of what he's talking about, here's a small picture of what I used to play with before I got older and practical.

Had 17 PSI running through it for quite some time. It was way easier to tune though, lol. Toss on a MAF extender and plug in your SCT and you were on your way.

 

[Robb235]

We're saying the same thing bro.







No, you're right. It does play it's part. I was simply replying to the guy I quoted, as it seemed he thought that the MAF somehow directly dictated the timing curve.







Well, since I wasn't sure and it didn't sound like you were positive either, here's what I turned up.....



4x4Wire - Tech: Understanding OBDII Engine Systems and Fuel Mixture Control



It sounds like you can do 35% before getting a MIL. So you might be onto something with tricking the MAF as far as fuel trims go. However, it looks like you have a fairly small range of voltage to play with before tripping a light, which was part of my original question.





And for context, so you don't think I'm just some dumb guy that doesn't post much and may not have an idea of what he's talking about, here's a small picture of what I used to play with before I got older and practical.

Had 17 PSI running through it for quite some time. It was way easier to tune though, lol. Toss on a MAF extender and plug in your SCT and you were on your way.

Wow 35%, didn't realize it was that much. Almost tempted to pop those 315cc injectors in there just to see what happens lol.

That's one thing that really irritates me about these Toyotas, no way to tune the ECU itself. You have to resort to piggybacks and try to keep the ECU fooled. I get jealous when I read other forums, and all they have to do is plug in HP Tuners or something, and they can change any part of the ECU. How nice that would be.

Sweet truck by the way, I bet that thing was loads of fun to drive.

 

[IBallEngineer]

Well, since I wasn't sure and it didn't sound like you were positive either, here's what I turned up.....

4x4Wire - Tech: Understanding OBDII Engine Systems and Fuel Mixture Control

It sounds like you can do 35% before getting a MIL. So you might be onto something with tricking the MAF as far as fuel trims go. However, it looks like you have a fairly small range of voltage to play with before tripping a light, which was part of my original question.

Good link! I was originally trained on closed loop back when Toyota had no fuel injected vehicles in the NA market. I was using a dwell meter to check the duty cycle of the solenoid in the carburetor of the GM C3 system. I was also factory trained on Chrysler 2.2 Turbos, and all the Mitsubishi Mikuni systems. But that was in a land far far away, or a time, that land forgot, or before the world was round or something like that. I don't normally participate in these type of threads, but I enjoy learning and relearning the theories.
:ranger:

 

[Cree]

Sweet truck by the way, I bet that thing was loads of fun to drive.

It would pass everything except a gas station.

Really looking forward to seeing where you end up with this thing when finished. Especially if you put it on a dyno and get some data.

 

[JayRolla]

The larger injectors are needed because whether supercharged or turbo'd, you will quickly max out what the stock 240cc injectors can flow, especially higher up in the RPM range. Same idea with the 7th injector kit. In order to run richer than 14.7 in closed loop, you'd have to use a piggy back of some kind that fools the O2 sensor, which you can get from URD. Eventually I'll look into doing something like that.

As far as saying that the MAF doesn't determine timing, I don't know that I agree with that. I believe that it indirectly does. I could be wrong, but I'm pretty sure that timing advance is heavily influenced by the calculated load on the engine. Calculated load is a value you can measure with a hand held scan tool (like a Scangauge2 or iPhone or Android app), and is calculated by TPS, MAF, RPMs, IATs, etc.. If the ECU is "fooled" into thinking it's taking in less air than it actually is, then it would report a lower Calculated Load value, and therefore advance timing. That's my take on it anyways. If you're able to disprove my understanding of this, feel free to, I love discussions like this.

Also, I'm pretty sure the ECU can go as far as +20% or -20% on the Long Term Fuel Trims. Any more than that, and the ECU will pop up with a "system too rich" or "system too lean" CEL.

Piggy backs trick the maf not the o2 sensor. The maf determines the tune. If our ECUs work like other ECU's ive tuned then you have closed and open loop. The ecu will advance timing as long as there is no detonation. Once you get some knock it will hold timing and if it gets more then it will retard. But thats usually a turbo ecu. Since this is not turbo stock then you may be right that it will keep advancing timing but hopfully retards when it knocks.

The injectors you use hopefully wont get you stuck in closed loop. The biggest problem is if your trick it enough the ecu will never know its getting enough airflow to open loop which will give you a different timing curve. If you get stuck in closed loop you will get crazing timing, with boost which means bye bye motor.

But again I think e85 would be the best setup for this.

 

[Robb235]

Piggy backs trick the maf not the o2 sensor. The maf determines the tune. If our ECUs work like other ECU's ive tuned then you have closed and open loop. The ecu will advance timing as long as there is no detonation. Once you get some knock it will hold timing and if it gets more then it will retard. But thats usually a turbo ecu. Since this is not turbo stock then you may be right that it will keep advancing timing but hopfully retards when it knocks.



The injectors you use hopefully wont get you stuck in closed loop. The biggest problem is if your trick it enough the ecu will never know its getting enough airflow to open loop which will give you a different timing curve. If you get stuck in closed loop you will get crazing timing, with boost which means bye bye motor.



But again I think e85 would be the best setup for this.

Been wondering if throwing on the 315cc injectors and just filling up with E85 is the better option. I assume the stock fuel lines will handle it ok. I would definitely have to plan out my road trips more carefully to make sure I have E85 to fill up with. Or carry extra fuel in jerry cans.

 

[JayRolla]

Been wondering if throwing on the 315cc injectors and just filling up with E85 is the better option. I assume the stock fuel lines will handle it ok. I would definitely have to plan out my road trips more carefully to make sure I have E85 to fill up with. Or carry extra fuel in jerry cans.

I ran e85 for many many years. It wasnt that bad finding gas stations. My brother just had all his SS lines fail from running e85 but took 10+ years before his fuel lines and fittings started to fail. He is now running nascar rated lines and fittings that has no parts that should be effected by alcohol.

But it was bad. All the insides of the SS line just poored out of the hose when we removed it. All this material was clogging up his fuel filter and causing a lean condition at high RPMS. He almost melted his motor.

I would not run e85 without a wbo2 to watch for lean conditions.

 

[Robb235]

So Santa Clause stopped by today.

 

[jeff88]

Ooooh shiny!

Maybe I missed it and rereading the thread doesn't produce results... what set is that and how many pennies?

What are the specs? Pre-turbo pipe size, post-turbo size, etc.