New Turbo, Issues, Resolved

[z-ya]

A few weeks ago I finally go my turbo 240Z back on the Dyna Pack for tuning. I recently upgraded the turbo from a T04B/T3 stock to a T04E/T3 stage 3. I also added a 3" exhaust. The new turbo use the Ford style built in waste gate.

 

The main issue I encountered with boost creep. The boost would continue to climb no matter what I se the boost controller to. After much fiddling on the dyno, I couldn't get the boost to be stable. Here is the final dyno chart:

 

 

 

A few days after the dyno tuning, I decided to take it all apprt again and look at the waste gate port in the turbine housing. What I found was that the hole in the turbine housing was about 1/8" smaller than the flapper all around. So I ported the hole so that it was almost the same size as the flapper (about 1/16" difference). I also smoothed the transition between the turbine inlet and the waste gate hole.

 

All this effort was worth it. It now hits 15psi at 3000RPM, and holds it all the way to redline.

 

Here is the engine configuration:

 

- Stock L28ET with P90A (hydraulic) head

- T04E/T3 stage three

- 3" exhaust with one 12" glasspack

- 15psi

- Wolf 3D 3.0 EMS

 

I will get it back on the dyno soon and post a new dyno plot. I expect to see more torque at the lower RPMs, and about the same amount of power.

 

Pete

[cygnusx1]

Hmmm...and I have my head off right now, the dremel is still warm from porting the intake and exhaust manifolds....my T3/TO4B SuperV is sitting right there on my downpipe, only four bolts away from being ported....and now you post this!

 

Don't make me pull my turbo and port the wastegate.....

 

How can I resist!

[z-ya]

Didn't want you to miss out on the fun ! I had to pull the exhaust, steering shaft, etc. to drop the turbo out from the bottom after putting it all back together the week before! Worth the effort though.

 

You port may be large enough. Take the waste gate off, and put something on the flapper (I used silver paint) to mark where it is closing. Then put it back on and close the flapper. This will show how much bigger the flapper is than the hole.

 

If the port ends up being too small, you will not get full boost until much higher in the RPM band (see plot). I had no boost controller in when I did this run. Didn't hit max torque until 5000RPM. Now I'm hitting the torque peak at around 3000RPM.

 

 

Pete

[Tony D]

Didn't hit max torque until 5000RPM. Now I'm hitting the torque peak at around 3000RPM.

 

Guys with an N/A making that kind of power would accept that first eventuality. Boy, are you picky, Pete!

[Brad-ManQ45]

z-ya:

 

Great news on the new turbo! You left out what trim the compressor was (50,57,60?).

 

Also, I'm a bit confused as far as your stating that porting the wastegate hole in the turbine housing allowed you to get full boost quicker.

 

The only effect this should have is to avoid boost creep due to not enough exhaust flow able to bypass the turbine section due to the smaller opening.

 

Now if you used a grainger valve to keep boost from the wastegate until just before it's supposed to open, I would say that that was a good reason for getting full boost earlier. Either that or increasing spring tension....

[z-ya]

Guys with an N/A making that kind of power would accept that first eventuality. Boy, are you picky, Pete!

 

NA guys making 300WHP are happy to have ANY torque below 5000RPM!

[z-ya]

z-ya:

 

Great news on the new turbo! You left out what trim the compressor was (50,57,60?).

 

Also, I'm a bit confused as far as your stating that porting the wastegate hole in the turbine housing allowed you to get full boost quicker.

 

The only effect this should have is to avoid boost creep due to not enough exhaust flow able to bypass the turbine section due to the smaller opening.

 

Now if you used a grainger valve to keep boost from the wastegate until just before it's supposed to open, I would say that that was a good reason for getting full boost earlier. Either that or increasing spring tension....

 

The compressor is a 50 trim. Internal waste gate.

 

It was boost creep. The waste gate hole was not large enough to bypass enough exhaust pressure to hold the turbine RPM steady. The plot above was taken without any boost controller. If I had my boost controller in there set at it's normal 15psi, the boost would shoot to 20+psi.

 

Pete

[big-phil]

I had to port my holset to just about the size of the puc to get rid of boost creep. But she holds steady now. Of couse I made a small video of it:icon31:

[Evan Purple240zt]

I have the same turbo in a 60, and it creeped BAD using the internal WG hole. Open that badboy up as much as you can!!

 

Evan

[ktm]

Pete, that is very odd that you experienced boost creep. I have no problem whatsoever hold 22 psi all the way to redline using the stock wastegate that came with my Garrett T03/04E 50 trim Stage 3.

 

I hit full boost (22 psi) by 3200 rpms as well.

[Brad-ManQ45]

OK z-ya, I didn't read into your first post that you were getting 15 PSI at 3000 rpm...

 

Now if your dyno graph represents the power you were making WITH boost creep, then you SHOULD wind up (assuming the same 15 PSI setting) with a bit less HP.

 

I guess I'm still a bit confused over getting a bit more low-end torque next time - unless you put a stiffer spring in the wastegate actuator, it will still start opening at the same time unless your boost controller also adds a bit of boost pressure on the back side of the diaphragm (to help keep the wastegate closed before full boost).

 

Just wanting to understand...

[z-ya]

The last dyno run I did no boost controller was present, and the stock actuator opened up the waste gate at 8psi around 3600RPM. The boost continued to creep in a linear fashion, The peak torque hit around 5200RPM. I let off the throttle on the dyno at 15psi (5600 RPM).

 

Now since the boost creep is fixed (opened up the waste gate hole) and the Dawes boost controller is back in there, it hits full boost (15psi) at 3000RPM. Since it made close to 320ft-lbs at 3000RPM on the old turbo, I am expecting it to make around the same on this one. Since I let up on this dyno run at 5600RPM (15psi), I am expecting to actually make a bit more power letting the dyno run to 6500RPM or so. I expect the power to start dropping off around 6000RPM. As you can see from the plot, the power was continuing to climb (along with the boost) up until I let off at 5600RPM.

 

Pete

[cygnusx1]

(Sidebar about boost controllers for those that want to skip ahead.)

 

There are two types of mechanical boost controllers. Ball-Spring and Bleed. Both of these are devices that modulate the pressure that goes to the wastegate actuator.

 

The dawes valve will get you that low end boost. I believe the Dawe's is the Ball-Spring type which will get you that fat, low end boost by completely clamping the wasetgate shut until you reach target PSI. By clamping the wastegate shut the boost builds more quickly. I don't mean physically clamping. The Ball-Spring valve keeps any boost signal from getting to the wastegate actuator untill the boost lifts the ball off the seat. This allows the wastegate to blow open and bypass exhaust pressure to maintain setpoint. The wastegate is either Closed or Open, with very little modulation.

 

The Bleed boost controller has a needle valve that you can adjust. It allows the wastegate to float open at anytime during the boost curve, as long as boost is over the spring pressure of the actuator. With it, you can modify the rate at which the gate opens to control the boost curve shape. The wastegate can modulated from Closed to Open, in a controlled manner, by turning the needle valve.

 

 

MAXIMUM spooling is achieved with the wasegate shut, forcing all the gasses through the turbine. This does not necessarily equate to maximum power. Some engines might like NOT to blow through the turbine all of the time, and might make more power in certain RPM ranges with the wastegate partially open. There is no BEST solution. That's why you test and tune.

 

Oh yeah...boost creep. Well, the wastegate is a port that lets the exhaust bypass the turbine to limit boost. If the port is too small for the amount of exhaust, it can't let enough out. What happens is that the excess gasses go back through the turbine and over-spool it. This builds boost in a runaway scenario which can be dangerous.

[z-ya]

I found the dyno plot for the T04B/T03 (stock turbine):

 

 

This is the kind of torque curve I am seeing now with the WG ported.

 

Pete

[Tony D]

I would tend to disagree about the ball-spring regulator being non-modulating. While it's true the thing holds the wastegate closed till the spring-cracking pressure is reached---after that point it functions normally as a 'seethrough' device on-boost, letting the wastegate do it's thing. It doesn't just pop open and stay there, it will pop and let some air in, then close in a rapid cycle bringing it up to full pressure like any other spring-regulated pressure regulator would do. There is an orifice in there that can be tailored to snub this action on rise, as well as drop in manifold pressure.

 

What you will see, is increased turbine speeds on drop-throttle as (depending on where you take the signal---mine is at the plenum) when that plenum goes to vacuum, the spring ball (which actually has a bleeder hole downstream to allow wastegate closure) will close and hte WG will close at the rate that the bleed hole will allow. If you feather the throttle slightly, on a WG with no spring valve in it, it may crack the WG slightly, while the spring valve equipped line hold pressure off the diaphragm allowing for faster re-spool.

 

The spring check-valve functions exactly the same as your FPR: Spring pressure over signal against contolled pressure (plunum).

 

If you have a bleed hole too small on the downstream side, you can have problems at lower boost pressures (even higher ones) of the WG 'sticking open' on drop-throttle and the turbo boost response going to hell. Small bleed hole will give you the 'open or closed' feeling on boost rise, but will conversely be very sluggish to respond on multiple throttle applications like feathering or WOT idle WOT in quick succession (like a burnout or doing driving tricks).

 

BAH! It's time for lunch and I have a meetting I have to go to. But I have been a convert to the Spring-Check Style Controllers due to their nice on-boost speedup of the turbine. After boost is on, they should act transparently if their bleed orifice is sized correctly. Valving the orifice on the spring-style will allow you some trim as to how the wastegate closes on rapid throttle movements mostly, but it's really splitting hairs. Bigger orifice will allow some creep over set pressure on initial rise, but eventually it will settle. Valves on the orifice can be plugged with dirt, making for some 'tuning issues' after time has passed...

 

I have put spring-style valves in all my turbo cars---even if it's only set to stock boost. The torque rise from that closed wastegate makes for much more drivability when you are not downshifting to make threshold rpms. Lazy Bastard that I am, I like this...

[cygnusx1]

I found the dyno plot for the T04B/T03 (stock turbine):

 

 

This is the kind of torque curve I am seeing now with the WG ported.

 

Pete

 

 

Very Nice!

[Pyro]

What t04b turbo was it? h3, v1/v2, ect???

 

what was the boost difference between the two turbo's?

 

do you feel it was the turbine (stock vs stage 3) or the compressor (B vs. E) that made the difference?

[z-ya]

What t04b turbo was it? h3, v1/v2, ect???

 

what was the boost difference between the two turbo's?

 

do you feel it was the turbine (stock vs stage 3) or the compressor (B vs. E) that made the difference?

 

T04B 60 trim. About the same boost level (13-15psi). It was the stock turbine that was restricting exhaust flow. With the stage 3 turbine and 3" exhaust there is nothing holding it back.

[Brad-ManQ45]

z-ya:

 

The TO4B has either an S-3 trim or a H3 trim or a V1/V2 trim, unless you were running one with the 60-1 compressor wheel....

 

for instance, I'm running a Turbonetics turbo I purchased in '94 - a water cooled center section with a .70 A/R compressor housing w/S3 trim and a clipped turbine.

 

Do you still have the old turbo to measure the compressor wheel?

 

All is clear now as to why you were making the projections you were - a lack of information in the original post had me wondering...

 

I bet you're happy...

 

I still have a problem with your relating the change in low end torque curve to the porting of the wastegate though...the low end would have to do with the ball and spring boost controller (I call 'em grainger valves). Once you achieve full boost and the ported 'gate keeps boost where you want it, yeah - you're gonna pick up some top end!

[z-ya]

For some reason I though the trip of the T04B was 60. I looked at it last night, it is .6 A/R. Do you know what the trim might with with this A/R?

 

With the ported WG hole, I can now control the boost level. With it un-ported, there was not enough bypass.

 

Before porting with the ball-spring valve in there set so the boost was 12psi on the old turbo, it would boost to 12psi at the normal rate, and then climb to 20psi very quickly. Without any controller in there, it would boost to 8psi, and then gradually climb to 15psi as RPMs increased. If I didn't let off, it would have continued to climb. Even though the WG was opened (I verified this using the video camera while doing a pull), the boost continued to rise. With the ball-spring valve in there, the turbine is spinning at a higher RPM for a given engine RPM, so it is closer to a run away situation. This is why it climbs quicker to 20psi with the vale as compared to without.

 

Make sense?