1984 Executive Sedan Turbo>*

[Vigo]

Yeh the thicker you put it on, the bigger the wrinkles. To be honest this last valve cover probably would have come out pretty well if i hadnt started with less than a full can. I got my base coats down great with even coverage and small wrinkles but it seemed like i couldnt get enough on there to get big wrinkles before the can ran out. Also, it got uneven-looking with the last coat, which i dont understand because i put it on even and the earlier coats were even.

[Vigo]

In the process of finding and cleaning up the exhaust studs for the head i realized i had broken one off in there and forgot about it.. i should probably fix that. I want to get the manifold on there so i can mock up the stock vnt i have, to check clearance for my wastegate idea.

This motor has been sitting here almost completely done for months.. I just need to mock up and then perform the wastegate mods and then get the new turbo put together and balanced before i can bolt it to a trans and hang it in there.

[Vigo]

So with this upgraded compressor side i always figured the main bottleneck in the setup was going to be the stock turbine side.. and today i got the itch to measure the exducer on the VNT turbine wheel and compare to the exducer on the Stg1 (stock) T3 turbine wheel (which has been dyno'd a LOT).

Turns out the VNT turbine exducer is only 2mm smaller than the Stg1 T3 wheel. The difference is much smaller than i would have guessed! By area, the 2mm smaller is about 10% smaller overall, but with the superior turbine wheel design i have to wonder if it isnt a wash.. if the stock VNT turbine side doesn't flow just as well as the stock-style garrett t3.

The turbine housing itself is a .64 a/r. I dont have the housing with me so i didnt consider that part of the equation tonight.

Also, when i was trying to find the exducer number on the internet to verify that the VNT uses a regular old t25 turbine wheel, i kept coming up with a ~41mm number instead of the ~46mm i measured. Turns out most of the t25 numbers out there are off of DSM t25s that have a smaller turbine wheel.

I also noticed someone point out/postulate that the garrett GT turbos ending in 71 (i.e. GT2571) use the old To4B compressors. I looked at the To4B compressor wheel specs and my wheel matches up (within ~1mm, i blame loose measuring margins) with the To4B V-trim wheel. I already suspected that the cover for it was a To4B cover. I looked at what google images i could find of that wheel and they do look the same.. 8 major fins and all that.

So, knowing there have been several 300hp dynos on stg1 t3 turbines, and knowing i have a to4b V-trim, i plugged a 300hp 2.2 into Frank's turbo calculator, picked the v1/v2 trim turbo (what is this v1/v2 stuff?) and got this:

Now, that shows it surging, but i dont actually know where this thing is going to spool, so im not worried about that.I can actually adjust the rest position of the vane arm to set my minimum boost rpm anyway if it surges, but since the comp wheel is SO much bigger than the turbine wheel im guessing it wont spool fast enough to surge. At the last data point there it looks like i'd be running it pretty close to its max efficiency at 300hp, so that's a plus.