Thread: Best place to fit MAF sensor in 4BD1T for boost guage

Originally Posted by Blknight.aus

ID go in the ally manifolt its thick enough to drill and tap straight off.

I also setup the turbo wastegate control to actuate from the manifold and the boost compensator to actuate off of the bleed point on the turbo thats usually used for the wastegate.

loctite 567 is your friend for this job.

Thanks Dave.
For some reason my turbo doesn't have a bleed point. Instead it bleeds from the pipe just after the turbo. The boost compensator/blow off valve is welded to the intake pipe just before intake manifold.

Does anyone know why the bleed point supplying boost for the actuator has a t-piece to also feed back to the low pressure side btw air filter and turbo?

Originally Posted by rar110

Thanks Dave.
For some reason my turbo doesn't have a bleed point. Instead it bleeds from the pipe just after the turbo. The boost compensator/blow off valve is welded to the intake pipe just before intake manifold.

A BSPT plug fits that hole in your intake pipe. Mine used to vent at 15psi, I fixed that

Originally Posted by rar110

Does anyone know why the bleed point supplying boost for the actuator has a t-piece to also feed back to the low pressure side btw air filter and turbo?

My guess is that's the bleed from your boost controller. I suggest ditching all that junk and setting boost by adjusting the wastegate actuator.

Originally Posted by rar110

Thanks Dave.
For some reason my turbo doesn't have a bleed point. Instead it bleeds from the pipe just after the turbo. The boost compensator/blow off valve is welded to the intake pipe just before intake manifold.

these are the ones you need to swap around. As the air moves through the induction system post turbo restrictions and heat loss (if you have an intercooler, Im keeping this generic) will lower the boost pressure so the best place to put your boost control sensors (MAP/Turbo waste gate actuator supply) is as close to the intake side of the engine block as possible. if you have say 2psi of loss in your intake system (just an example) and your waste gate/electronic control is set to cut you off at 15psi of boost (again just an example) and you take the supply (bleed point) from right after the turbo the turbo will stop pushing at 15psi, then you loose 2 psi though the intake system so the pistons are only seeing 13psi of boost pressure. By putting the supply for the waste gate actuator/electronics as close to the engine block as you can get it the turbo will now push in 17psi of air to make up for the 2psi loss giving you 15psi in the pots which is a good thing for your power and EGT's.

Conversely if you have a boost compensated engine the best place to put the supply (bleed point) for the boost compensator is close to the turbo preferably in a bend with the orifice pointing back up towards the turbocharger. This means the boost compensator sees the pressure coming off the turbo before there's any losses and will wind up the fuel earlier.

Originally Posted by rar110

Does anyone know why the bleed point supplying boost for the actuator has a t-piece to also feed back to the low pressure side btw air filter and turbo?

you will possibly find that this also has a restriction in it and will be being used to "buffer" the pressure thats getting onto the actuator to prevent it from "pulsing" during gearchanges or when your throttle control is erratic (like driving over a bumpy road)

I have had the boost compensator and boost guage in for about 2 weeks now. A few observations:

• The boost controller is not very precise. Im not sure it does anything but prevent the wastegate actuator from operating at all. I have it on a very low setting which is not supposed to change the set up, but it has. I think making the wastegate actuator adjustable would be better.
• Boost goes up and down according to how hard the motor is working. Which makes sense as the amount of air being pumped about depends on the amount of exhaust being pushed out of the motor.
• The overboost safety valve releases at about 16 or 17 psi.
• EGTs are now about 50 degrees hotter at idle after a run (about 180 degrees) and sit on about 350 degrees on the highway with no weight or tow.
• I dont notice very much increase in power from running higher boost, may be a bit more torque.

I was intending to measure the boost as close as possible to the intake manifold by fitting a barb to the steel section immediately before the intake manifold. However, I couldnt buy a nut with the correct thread for the barb, to weld to the steel intake pipe. So I ended up stuffing a lot of rag into the intake and then drilling/taping into the intake manifold. I also ran a vaccume cleaner on the inside of the manifold while drilling/tapping. It worked out quite well. The sensor is mounted on the firewall motor side.

rar110

The more I read the more it sounds like your setup has been done by a petrol guy and not a diesel guy.

Pressure pickup for your injector pump, as a rule is a single line from the pressure side of your turbo.

Why from the turbo and not the inlet manifold? Easy way is that regardless of pressure and temperature it just easier to tune your fueling if you pickup is from that side. You will have pressure drop due to resistance but this is a constant. You will also have pressure drop due to the intercooler doing what its supposed to do. This is inconsistent and will vary due to speed, pressure ambient temp etc etc. How ever you pressure gage only reads pressure and not Km3 which is what you really want if you want your fueling bang on. This is a product of pressure (density) and temperature.

Your pressure line you say is T off with a line into the air filter. This is as posted either to take out some of the pressure surging in this line. Surging that is usually associated with a throttle body and butterfly opening and closing. As you don’t have this you don’t need that other ( its a petrol trick). OR it could be there to trick your injector pump into under fueling. this is a possibility with the weird way your system is set up with a pop of valve.

your pop of valve, yes it will drop pressure and is often found on petrol motors to quickly dump air when the throttle is closed it also avoids a short period of very lean running and the risk of burning things and backfiring etc . None of this is a problem for you. just get rid of it as i suspect based on your previous posts that it is confusing the issue.

How it should work

As pressure climes. the pressure line to you injector pump tells the pump to add more fule, this in turn increases boost. More fuel more boost etc etc. until such time as the pressure over comes the spring in the waste gate. this bleeds hot gasses around the turbo limiting the turbo ability to produce more boost. Your injector pump is only effected by the pressure line so if the pressure isn’t going up the fueling isn’t going up. Simple.

With the pop off valve. the sanerio would be something like.

pressure climes, more fuel until the popoff vale opens. bleeding of air. in the mean time the turbo loses load but still has a lot of hot gas spinning it. it could start to sort of free wheel. not a good thing.

With the pressure line T off it could mean that you are constantly under fueling or that your fueling has been turned up to compensate. either way its all not Kosher and rather confusing. so best just junk the t bit and pop off valve and play with your fueling until that’s correct. Then look at your waste gate pressure and fueling if you want more GO.