BOOST Tuning

[mediumrareintexas]

I'm installing an ATI Procharger with 7 PSI boost. Do I really need to have the 2BAR support enabled to properly tune for this upgrade?

[tici]

Most SC cars are running fine with the stock MAP sensor.
I think you need an upgrade only if you run SD, otherwise the MAF will work fine for this amount of boost.

[mediumrareintexas]

Thanks for the response. I've been working on my speed density tune following the SD instructions in this forum. I had to stop because I need an emissions inspection which has expired. So I'm working on that right now. I'll get back to the SD later.

So if I'm doing SD, then you feel that I do need 2bar enabled?

[tici]

in SD the PCM calculates fuel depending on RPM and MAP.
If your VE table and MAP sensor can measure only up to 105 kPa the PCM will be blind when under boost and will keep using the 105 kPa values and go lean...

By the way, why SD? IS it really necessary for your mods? A MAF is not that bad at all.

[mediumrareintexas]

Based on what I have read, seems like SD is the way most people are going for better performance. But maybe that is wrong. I haven't seen any comparisons as to the benefits of SD vs MAF. I guess it is kinda like a discussion of open loop vs closed loop. Which is easier to tune and provide the best performance?

[tici]

SD is for when the car is so highly modded, that the PCM won't be able to handle it in the standard way. No matter how good it's tuned.
In SD you simply reduce the amount of parameters: maybe less perfect but with less troubles also.
In SD you can also remove the O2 sensors, than the car is 100% working with the VE table. Open loop all the time. Same as going back to a carburator
It all depands on the mods and on your goal: daily drive for every weather / traffic condition or a race car?

[mediumrareintexas]

I like the back to carburetor idea. How do you know if your VE table and MAP sensor can measure greater than 105 kPa? I think I did read somewhere that I need to replace the MAP with a 2bar MAP. But, I haven't gotten that far yet.

Sounds like SD is the way to ensure the PCM will not be blind when under boost and will keep using the 105 kPa values and go lean.

[tici]

Sounds like SD is the way to ensure the PCM will not be blind when under boost and will keep using the 105 kPa values and go lean.

Only if you don't have a MAF.

I don't know HPTuners, but for sure you need a MAP sensor that covers the entire pressure range and a software that can handle that too.
This of the carbutator works, but forget mileage, emissions, wheater changes and so on.
The problem of boost + MAF is that after a certain level of power the MAF will reach it's limit. Either you change the MAF (& c alibration) or you go SD with a 2 bar MAP.
With the stock VE table & MAP it will be fine when using the MAF because in that RPM range the PCM won't consider VE but just the MAF.

[Chris@HPTuners]

you can stick with the MAF until it maxes out, generally above about 10psi on a 5.7L.

If you do any boost tuning in SD then the PCM cannot correctly calculate the airflow (and hence the fuelling) once you get above 105kPa (atmospheric). With our 2bar enhancement you need to install a 2bar MAP sensor and the VE table is modded to include areas above 105 kPa.

Chris...

[DanaliHD]

would it be pointless to install a 2 bar without upgrading to the 2 bar software? wouldn't we all still be better off with at least a 2 bar map sensor whether we are tuning or not?

[tici]

Isn't the 2 bar MAP having a 0-5V signal?
In that case you'll have to have the new software because you'll have 2.5V at 100 kPa - the PCM will think you are at 50kPa :P

Are you concerned of putting too much stress on the stock MAP sensor? THat would be a point...

[Chris@HPTuners]

would it be pointless to install a 2 bar without upgrading to the 2 bar software? wouldn't we all still be better off with at least a 2 bar map sensor whether we are tuning or not?

it is pointless

[mediumrareintexas]

So let's see if I have interpreted this correctly....

1. SD tuning is only necessary if the MODS performed have exceeded the capacity of the PCM to control normally.

2. MAF tuning is sufficient unless the BOOST exceeds about 10 PSI on a 5.7L.

3. The HPTuners 2BAR enhancement is not required unless the MAF maxes out.

4. In order to use the HPTuners 2BAR enhancement, a 2bar MAP sensor must be installed and the VE table is modded to include areas above 105 kPa.

[tici]

What are your (planned) mods?

[Chris@HPTuners]

So let's see if I have interpreted this correctly....

1. SD tuning is only necessary if the MODS performed have exceeded the capacity of the PCM to control normally.

2. MAF tuning is sufficient unless the BOOST exceeds about 10 PSI on a 5.7L.

3. The HPTuners 2BAR enhancement is not required unless the MAF maxes out.

4. In order to use the HPTuners 2BAR enhancement, a 2bar MAP sensor must be installed and the VE table is modded to include areas above 105 kPa.

basically yeah. However, remember our 2bar enhancement also offers the ability to tune the fuel based on MAP in addition to the standard RPM based (PE table) method. Some people like to set the fuel to richen as soon as boost is achieved or use it as a safety net against hitting boost and staying in closed loop.

Also, remember the small 75mm LS1 MAF is restrictive and trying to suck even more air thru it makes things even worse. Also, keep in mind on turbo setups that when you close the throttle and have a long intake path (via an intercooler) the turbo's will continue to draw/blow air thru the MAF, however this air is not going into the engine, it is in effect pressuring the intercooler. This can lead to rich conditions on throttle closure at idle (eg. after a burnout as the turbo's spool down). SD doesn't suffer this problem, however, SD is very reliant on *accurate* IAT readings and you need to be especially careful that you are not reading aluminum temperature rather than air temp when you position the sensor - this is especially true for valley fit setups.

Chris...

[tici]

How accurate is a blow-through MAF?
Many setups (like Vortech) measure the air before the blower, the unused air is recirculated so that the MAF will measure the real air quantity.
The drawback is that this air gets hot, especially ar idle or low load.

[Chris@HPTuners]

How accurate is a blow-through MAF?
Many setups (like Vortech) measure the air before the blower, the unused air is recirculated so that the MAF will measure the real air quantity.
The drawback is that this air gets hot, especially ar idle or low load.

on a s/c setup it makes no difference since the wheel is directly attached to the engine, only an issue on turbos. Many avoid blow thru MAF setups cos if the inconvenience of having another couple of joins to secure on the pressure side and also the perceived frailty of the MAF when on the high pressure and hot side (never seen it proven personally).

I dunno what you mean by unused air is recirculated. Either you're trying to make boost or you're not. Some systems have a bypass that unloads the rotors/impeller at light throttle to regain mechanical efficiency but thats about it. Under load it is completely closed otherwise you can't make boost.

[tici]

I dunno what you mean by unused air is recirculated. Either you're trying to make boost or you're not. Some systems have a bypass that unloads the rotors/impeller at light throttle to regain mechanical efficiency but thats about it. Under load it is completely closed otherwise you can't make boost.

THat's what I meant. Vortech has a Bosch bypass valve that will open if you apply vacuum to the membrane. This is connected to the manifold.
Under boost the membrane closes and keeps the pressure. When you close the throttle you have vacuum in the manifold and the membrame opens: the charge air goes back to the suction pipe of the SC.
At idle or low load this air will pass several times trought the blower and get hot.
I'd prefer a blow through MAF or SD and discharge the bypass air so that the system is always cooled by new fresh air, but this involves either a different piping or a totally different tune + 2 bar MAP.
I'm set with my car, everything is fine and I don't want to start over with new things, but if it was a new project like mediumrareintexas I would consider something different than what I have.

[Chris@HPTuners]

discharging the bypass air would mean you have a pretty serious vacuum leak when the bypass opens. No way around it without using an electro-mechanical clutch of some sort on the blower to actually stop the rotors/impeller. Believe it or not this is getting a serious look at by a lot of euro manufacturers as they try and come up with low down torque and no lag combinations vs. traditional turbocharging.

I dunno if you guys have a seen a movie called Mad Max (i think in the US it was called Road Warrior or something), it was released in 1979 and the car featured an electric switch that Max (Mel Gibson) would hit when he needed some extra grunt. The switch supposedly engaged the 6-71 sitting atop the 351 clevo in the old girl which was enough to outrun the baddies who were hitting the NOS... classic stuff

[mediumrareintexas]

The ATI procharger I'm installing has a bypass valve connected to the vacuum. As boost is applied, the valve closes. Seems to me that if I adjust the valve so that it is only half open before boost is applied (i.e. idle), then I would get boost earlier in the rpm cycle because the valve would close earlier. That would probably also create a lean condition.

Currently planned mods are: 7psi procharger, racetronix fuel pump, 42lb injectors.