Hey everyone, I have an 88 turbo 5 speed. It has a full 3 inch exhaust, intake filter and a greddy profec b spec 2. I have seen the thread about tuning it, but i cant seem to figure it out. Every time i shift up while im in it hard, i hit fuel cut. I have tried tuning it following the intructions in the other thread, but those are for an EVO i believe, so they are not as detailed towards mkiiis. Is there anyone who has a profec b spec 2 that could give me their percentages of gain, etc, who is running around 11.5psi (or close to fuel cut) on the stock turbo? Or can anyone give me a better way of tuning it?:1zhelp:
Fuel Cut
- Thread starter eman2289
- Start date
eman2289 said:
The mk3 is over fueled from the factory to the point of not being funny, WOT your at less than 10:1 afr. The air screw makes up less than 10% of the area of the main passage so turning it out should not put you in any danger. Unless you already have an air leak you don't know about or 1 or more of your injectors isn't flowing like it should. I have my screw backed all the way out and can pull 15psi in fith gear without fuel cut.
If you feel uncomftable with screwing it right out just turn it out a few turns should give you a psi or so more to play with.
I'm waiting on my widebade to arrive in the next few days so i could get some data on this, do some pulls with the screw in the factory position then screw it out and do some pulls and see what difference it makes.
Believe me, ive done that. But its not just a matter of turning it down, once you turn down the base, you also have to mess with the gain. Its confusing. Im not worried about 15psi in 5th gear. Im a quarter mile guy and im worried about not hitting fuel cut, but being able to hit just below it and hold it there. BTW i have tried shifting both ways, not letting go of the gas and letting go of it.cactus_mole said:
All the Profec does it adjust boost. it's not tuning anything. Fuel Cut is a failsafe so you don't push the fuel system past what it can handle and run lean. The only thing you can do with your setup that is safe without a wideband is to turn the boost down. Every car hits Fuelcut at different boost lvls. So that may be the max your car can do.
One thing you need to check for is a boost leak, if you have a leak that could cause fuelcut at lower boost. If you have none then you are out of luck until you get a wideband and something that you can do some real tuning with.
One thing you need to check for is a boost leak, if you have a leak that could cause fuelcut at lower boost. If you have none then you are out of luck until you get a wideband and something that you can do some real tuning with.
I should'nt have used the word "tune". All I am looking for is the proper way to "set-up" the Profec B Spec 2 in order to not hit fuel cut. I was looking for the numbers that people have put their gain and set values to. I am not looking to bypass fuel cut, I am trying to stay just under fuel cut.
On my previous set up , all i had intake ,3" turbo back and 2" intercooler hard pipes + no boost leak . I hit fuel cut at 14psi and back out screw on stock afm i hit fuel cut at 16 psi of boost. ( killed stock 18 years old turbo in 12 months with that 16 psi of boost).:naughty:
Ok. You dont have the answer, thanks anyways.rumptis said:
For anyone else that is reading it, its not as simple as turning it down. There are 4 or 5 values that need to be adjusted in order to turn the boost up or down. All i am looking for is those values. Apparently no one has an answer, thanks anyways.
Well if you hit fuel cut at 11.5 psi that's mean you have boost leak some where . you need to check for boost leak and vaccumm leak first, vaccumm leak some time also boost leak . Tunning doesn't solve your fuel cut problem ;but if you have boost creep problem then porting wastegate is way to go .
I feel sorry for this poor guy, he has tried to ask us all how to adjust his boost controller, and all he gets is sarcasm and advice about everything but the boost controller.
I'll try and help. First off, do you have the manual? If so, you should have a pretty good understanding of how to navigate between modes. From my
experience, it is best to turn the unit off and make a few WOT pulls. The peak boost will be recorded on the profec. once you know where your stock boost level really is, you can then begin to make small adjustment to your SET boost percentage. Also if you haven't already done so, it might help to set the controller to read in PSI instead of KPA (unless you are more confortable reading KPA). You must also know that the adjustment made to the Lo setting
only affect your Lo settings and the same goes for the Hi settings. Therefore you must make adjustment under the setting that you plan to use.
So now that we got that out of the way, here is how I "tuned" one.
First understand that the percentage displayed when you make your adjustment under the SET boost setting is not based on a percentage of boost but rather the controller's duty cycle. This means that the valve which controls the boost will be "closing" that percentage of the time. so if the percentage reads 10% the valve will work less than if you set it to 100% (where the valve will remain closed all the time and max out your turbo...no good). In your case since the unit is already boosting too much, I would turn all of the settings down which relate to boost control. These settings are:
Set boost (displayed as SET)
Gain percentage ( displayed as GAIN)
Start boost (displayed as SET GAIN)
You should also make your adjustments in that order. Here is why:
Once you have selected either Lo or Hi boost, you will start by setting your desired boost level. Again this is under the SET mode and will be shown as a percentage while setting. once you have confirmed your selection, the screen will go back to your actual boost or vacuum reading. Start by making small percentage increases and looking at the boost pressure that it yields. Since every car is different, your percentage could result in a big or small impact on the wastegate. increase your percentage until you have gotten to your desired boost level. If you find that the boost just continues to rise as the RPMs go up, then increase the Gain by a percent or two. The gain will be used to maintain the desired boost level once you have reached it. If you turn the gain up too high, it will cause the boost to spike temporarily past the desired boost level. If this happens, just turn the gain down until the boost gets to where you want it, and holds there. Again make small adjustment so you can fine tune it. This brings us to the last adjustment for your desired boost level, the Start boost. This adjustment is made to speed up the boosting process. In essence, Start boost is there to reduce lag it is like a response adjustment for the controller. the higher you set it, the faster the controller will allow you to get to your desired boost level. They recommend that you set the Start boost close to the same percentage that you selected under SET mode. Although if you set it too close, the boost could spike. This why you leave this setting for last. Because if you have already found your desired boost level and you have adjusted the gain properly, there should be no spikes in boost. So what you do is, set the Start Boost to a percentage just below the point where a spike in boost would occur. Again make your adjustments gradually for maximum response without spikes in boost.
NOTE: A good way to check for spikes is by checking the Peak boost that the controller registered. If your boost is spiking up to the Peak boost displayed, but then dropping off and holding at a lower level, adjust your Gain or your Start boost depending on which step you are up to.
Of course the ProfecB2 has other features, which can impact your performance. Such features like the Warning setting and the Limiter can in fact act like fuel cut. The idea is to set the Warning to a level that you don't want you boost past ( 1% above your desired boost level since you are shooting for just under fuel cut), and if the boost spikes to the Warning level, the Limiter (if activated) will then cut the boost down by the specified percentage. You must set the limiter somewhere between 0% and 99% in order for it to work correctly. If you set it to 0 it will be deactivated and if you set it to 99 it will bring you back to stock boost. The percentage you select will be deducted from your original SET boost setting (desired boost level). So a 10% adjustment should result in your boost dropping by 10% of your desired boost level.
I hope this helps.
Wells.
I'll try and help. First off, do you have the manual? If so, you should have a pretty good understanding of how to navigate between modes. From my
experience, it is best to turn the unit off and make a few WOT pulls. The peak boost will be recorded on the profec. once you know where your stock boost level really is, you can then begin to make small adjustment to your SET boost percentage. Also if you haven't already done so, it might help to set the controller to read in PSI instead of KPA (unless you are more confortable reading KPA). You must also know that the adjustment made to the Lo setting
only affect your Lo settings and the same goes for the Hi settings. Therefore you must make adjustment under the setting that you plan to use.
So now that we got that out of the way, here is how I "tuned" one.
First understand that the percentage displayed when you make your adjustment under the SET boost setting is not based on a percentage of boost but rather the controller's duty cycle. This means that the valve which controls the boost will be "closing" that percentage of the time. so if the percentage reads 10% the valve will work less than if you set it to 100% (where the valve will remain closed all the time and max out your turbo...no good). In your case since the unit is already boosting too much, I would turn all of the settings down which relate to boost control. These settings are:
Set boost (displayed as SET)
Gain percentage ( displayed as GAIN)
Start boost (displayed as SET GAIN)
You should also make your adjustments in that order. Here is why:
Once you have selected either Lo or Hi boost, you will start by setting your desired boost level. Again this is under the SET mode and will be shown as a percentage while setting. once you have confirmed your selection, the screen will go back to your actual boost or vacuum reading. Start by making small percentage increases and looking at the boost pressure that it yields. Since every car is different, your percentage could result in a big or small impact on the wastegate. increase your percentage until you have gotten to your desired boost level. If you find that the boost just continues to rise as the RPMs go up, then increase the Gain by a percent or two. The gain will be used to maintain the desired boost level once you have reached it. If you turn the gain up too high, it will cause the boost to spike temporarily past the desired boost level. If this happens, just turn the gain down until the boost gets to where you want it, and holds there. Again make small adjustment so you can fine tune it. This brings us to the last adjustment for your desired boost level, the Start boost. This adjustment is made to speed up the boosting process. In essence, Start boost is there to reduce lag it is like a response adjustment for the controller. the higher you set it, the faster the controller will allow you to get to your desired boost level. They recommend that you set the Start boost close to the same percentage that you selected under SET mode. Although if you set it too close, the boost could spike. This why you leave this setting for last. Because if you have already found your desired boost level and you have adjusted the gain properly, there should be no spikes in boost. So what you do is, set the Start Boost to a percentage just below the point where a spike in boost would occur. Again make your adjustments gradually for maximum response without spikes in boost.
NOTE: A good way to check for spikes is by checking the Peak boost that the controller registered. If your boost is spiking up to the Peak boost displayed, but then dropping off and holding at a lower level, adjust your Gain or your Start boost depending on which step you are up to.
Of course the ProfecB2 has other features, which can impact your performance. Such features like the Warning setting and the Limiter can in fact act like fuel cut. The idea is to set the Warning to a level that you don't want you boost past ( 1% above your desired boost level since you are shooting for just under fuel cut), and if the boost spikes to the Warning level, the Limiter (if activated) will then cut the boost down by the specified percentage. You must set the limiter somewhere between 0% and 99% in order for it to work correctly. If you set it to 0 it will be deactivated and if you set it to 99 it will bring you back to stock boost. The percentage you select will be deducted from your original SET boost setting (desired boost level). So a 10% adjustment should result in your boost dropping by 10% of your desired boost level.
I hope this helps.
Wells.
No problem, do report back your result please. I'd like to know that it worked out ok. Also make sure that your vacuum line are good as they to could cause the boost to spike, if the come off the turbo/control valve. I'm that you understand that this nor any boost controller can control below your wasgate pressure. Stock pressure= base boost level. that will be the lowest boost level the wastegate will hold. So in essence, your Profecb2 can give you two more boost setting for a total of three. Something like, Base boost, mid boost, and High boost. The only two you could adjust via the profecb2 would be the Mid (Lo) setting, and the High (Hi) setting. So enjoy.