Turbo problems

[diggerdave]

hmm. I can easily hit 20 if I do that. Perhaps my own cheapo boost gauge is the problem. I've ordered a second hand one that promises to be better quality so I'll see what happens then

 

[Shayne]

How are you increasing boost , do you have a controller ?

 

[diggerdave]

MBC

I previously tried one of the cheaper Turboboost T types but that overboosted even on its lowest setting, leading to symptoms of fuel cut off (a bit like the feeling of hitting a rev limiter)

On the MBC even with the screw only slightly wound in I get 14/15psi when revving to redline while stationary and I can get 19/20 in maximum boost situations on the road with no sign of fuel cut-off

 

[diggerdave]

I've been following the FSM method of measuring boost. I don't know if this is the only or best way of doing it (like I say, newbie). I'd like it if there was a better way because it feels uncomfortable revving to 4600RPM...

 

[Shayne]

I swapped that blue actuator pipe pictured above for about a foot long length which is a job for Jap midget fingers but doable then put the turbosmart T from the turbo followed by the gauge tap which is closer to the actuator if that's any help ?

 

[diggerdave]

My boost controller is plumbed in exactly where you describe. My giant sausage fingers were no help whatsoever. However, my boost gauge is next to the inlet manifold/MAP sensor at the moment

 

[diggerdave]

So your boost gauge is between the actuator and the boost controller. I'll give it a go and see if my readings are any different

 

[Shayne]

Yeah if you tap into where i have the gauge can only show what pressure the wastetgate opens at , boost can't increase when its open because the pressure just gets dumped into the exhaust .

 

[Beau]

Revving the engine while stationary isn't the best way or in fact normal way of measuring boost. It has to be done on the road with a LOAD on the engine/turbo. A hill on a long stretch of motorway in top gear, foot down will likely show max boost. RPM doesn't necessarily correlate with boost.

My boost guage is plumbed in before the MAP sensor, I did this because I wanted to see what the ECU was actually getting. It's normal to get slightly higher pressure readings from the wastegate but this can be a false reading to what the engine is actually getting.

 

[Shayne]

I can't add that one up Beau , pressure cannot build unless its contained so even if the turbo was putting out 20 psi its just getting blown out the exhaust when the wastegate is open surely ?

 

[MarkW]

It can't build but you can loose boost through the intake and intercooler.

On petrol turbos boost is normally measured at the inlet manifold so you see the boost at the engine

 

[Shayne]

Yeah it can leak post turbo but that's not something to worry about but the guys are saying they get higher gauge readings at the sensor which doesn't make sense if the wastegate opens when it should ?

 

[Beau]

No, lower readings at the map sensors, not the waste gate side. And like mentioned above, you'll get a slight loss on vehicles with IC.

The turbo is a bit more complex than just a pressure pump. You have variables like the exhaust gas pressures which initially set the spool and get the pressure going. More gases = more potential boost pressure. Hence why when you're under load and call for more power, more fuel gets injected, bigger combustion = more exhaust gases which then spin the turbo more which then increases boost pressure further. This of course happens within a second, and if you had a boost gauge you would see how much fluctuations there are over the driving course in various conditions.

Not sure if I answered your question really...

 

[Shayne]

The way i see it the turbo is there mostly to boost acceleration times in our diesel trucks , floor the pedal and she rams as much air and fuel into the mix as it can to bring the revs up and maximum boost is a momentary thing providing the last 200rpm kick so to speak . When revs match speed the turbo is just an assistant to allow more efficient fueling .

The fuel cut is Toyota's defence against the fact the CT12B turbo is capable of so much more than our engine can cope with , people have them in Supra's and Mr2's !

Use your gauge at the gate to set the controller and the gauge is no longer needed . Shift it up to the sensor to see what post turbo leaks you have .

It's Dave's faulty gauge that confused me .

 

[Beau]

Although the turbo can handle more boost, I have read that once past around 20 psi, a lot of heat is generated which leads to diminishing returns really. Those NZ guys upgrade the internals for it to flow better and allow more boost without the extra heat. Then of course, there's also longevity which Toyota factored in, because I've not really heard of any turbo issues on these things...

 

[diggerdave]

Revving the engine while stationary isn't the best way or in fact normal way of measuring boost. It has to be done on the road with a LOAD on the engine/turbo. A hill on a long stretch of motorway in top gear, foot down will likely show max boost. RPM doesn't necessarily correlate with boost.

My boost guage is plumbed in before the MAP sensor, I did this because I wanted to see what the ECU was actually getting. It's normal to get slightly higher pressure readings from the wastegate but this can be a false reading to what the engine is actually getting.

So when people talk about 'boosting at 14 psi' being the maximum, they mean the maximum boost they can achieve under load? That seems to be how both you and Shayne are measuring it (although with gauges in different places).

What concerns me is that my gauge is showing 19-20 as my maximum boost, but there's no sign of the ECU cutting the fuel. While my gauge *might* be faulty, it won't be that far out surely? I'll try it again with my second gauge when it arrives.

I'm not that bothered as it runs right well anyway! I'd just like to solve the mystery

 

[Shayne]

I can spin the front wheels on dry flat tarmac so i think you would know if you were boosting at 20 Dave , put the gauge in to see where the wastegate opens and you might find your under 14 still , which would be a bonus because it means you can get more power than you have already .

I think 3200 is about the hardest i have ever pushed rpm in my truck .

 

[Beau]

That's correct, you only tend to achieve max boost under load. Revving the engine will hardly have boost go beyond 5psi on my gauge. cruising on a flat road at around 70-80mph has boost around 9-10psi. If I hit a long hill and ask more power to speed up then I can easily take boost from 10 to 14 psi in a second.

Plumb your boost line on the intake side and report back your boost levels. If the ECU isn't kicking in you're for sure not past 14 psi.

 

[Iwan]

Guy's! All I can say from quite a bit experience with the 1kzt (e). From when I first had one in 2005 is that you are totally limited with your fueling using the electronic VE style pump! It's limiting your progress with tuning i.e. you can't progress any further. What it is ... is what it is!

But even with a mechanical pump with the fuel turned right up there's limitations with it cause as Beau has said over a certain psi on the turbo gauge the egt's are too high and thats because the exhaust compressor on the CT12B is way too small (blocking flow) cause it was designed for lower end pickup and the only answer is to fit a variable vane turbo! Which will adapt to the high end use that your aiming for. A small exhaust compressor will raise egt's and contribute to the cracked head situation.

I've been dismantling the (e) pumps and compared to the mechanical pumps they're an empty box and I can't understand why they cost over a £1000 to buy a new one cause to me the only usefull parts are the cam plate and the 12mm plunger! Those (e) pumps are the devils work! I really don't like them at all. Why rely on an ecu when you can be mechanically independent! A bit like being in the EU lol!!

All from my experience!

 

[Iwan]

If you use the exhaust manifold off the 2.5 d4d which is a direct fit. Then it opens up many options. The turbo there is off a vw tdi v6. The variable vane garret turbo is well up for the job on the 1kzt! Just haven't had the time to persue it! You'd probably need a body lift to close the bonnet tho! Lol!