My DIY twin turbo build Gen 1 Viper - by AndyMac

6 minute(s) of a 25 minute read

So I put a fitting in the exhaust pre-turbo so I could measure back pressure today. I found that the back pressure to boost ratio is right around 2:1, even at 5500rpm. I did several pulls around 5-6psi and then a couple at 10 to 14psi. You typically want the ratio as low as possible, why still spooling the turbo in a timely fashion. 2:1 is acceptable, but getting to the upper limit.

Not saying these turbos are optimal, but they aren't as restrictive as some people have eluded to. I do think the power curve will peak early, but I do need to get to a dyno to check it out. I've tried using the HP calculator in the VEC logging software, but don't think the results are accurate.

Later,

10-30-2010

Few vids of the car

Right click, save as..

Shot inside the car turning onto the highway, 6-8lbs boost.

http://www.myturboprojects.com/viper...ost_run_01.wmv

Shot of the tach.

http://www.myturboprojects.com/viper...ost_run_02.wmv

Later,

1-22-2011

Been working on the car here and there the last few months. Built some manifolds to fit some GT45's and 60mm gates on the car.

Here's the start of the 4" exhaust off the turbo.

1-24-2012

Wow, guess it has been a while since I've updated... Lets add a few more pics, I'll see if I can do it in chronological order...

So, I got rid of the T3/T4's and went with two 70mm turbos.

Here is a pic with a "mock up" turbo, old turbo, and 60mm gate.

My 4" "muffler" lol, if you wanna call it that.

Pulled my heads to get rid of the paper gaskets. (They were still fine, but better get the MLS ones in there anyway.

Stock heat shield back on and pipes wrapped. You can see I had to move my filters to under the car now.

Monster exhaust wheel. (I like to think of it as traction control, or "boost by gear" lol)

Exhaust done

Tapped the block under the intake for a knock sensor. (for MSD Knock Alert)

That about wraps up the winter of 2010/2011... More to come

So, last summer I spent fighting some issues where the car wouldn't pull past 4800 rpm. I blamed it on my smaller turbos, but it still exists with the larger units and massive wastegates. I hit the dyno late last fall anyway just to see, and only managed 700whp by 4800rpm where it would start going way lean no matter how much fuel I put to it. (still stock motor, stock valvetrain, etc)

So, I finally figured out it was weak valve springs causing my valves to float under high load and lots-o-boost. Valve float sends raw gas and lots of air into the exhaust which shows lean on my WB and why I couldn't richen it up any. (Tip - o2 and WB sensors only read air content, not fuel, so if there is unburnt fuel in the exhaust, it doesn't see it)

Anyway, so Valvetrain time.. Roes dual valve springs and locks.

My home made valve spring compressor. To do this, you need to pressurize the cylinder so the valves don't fall down. You can see the line from my compression tester hooked to my compressor to keep the cylinder full of air.

New Harland Sharp rockers and hardened pushrods.

Also painted my intake and valve covers to something more appropriate.

Added fittings to my intake and redesigned my fuel system slightly.

Added a BAP

New Acer tablet running win7 to tune with

The car runs strong now, strong enough to shred gears doing a 3rd gear pull on the highway even though AFR's were 10:1 at the time...

That is about it I guess, going to hit the dyno before fall to see what kind of power I can extract from the new setup. 800whp should be a joke on 91 with 800cc's of water/meth. I kind of want to push my luck for 1k whp, but I don't want to trailer the car home from the dyno..

And here is a little media for this thread. Kinda goofin around on my first run at the AutoX..