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Our Twin Turbo analysis.

10K views 124 replies 17 participants last post by  Hass828 
#1 ·
As many know we built a twin turbo with the guidance of Mark Unchained. Got it going late in the season last year. Made way too much power. I was told it would by Mark and Hass. Had a few problems and eventually kept it in one piece.

Spit the belt driven fuel pump drive out one day testing. It lean popped but seemed OK. Had low boost one test session and found a silicon coupling was blowing loose under boost. lol. Lost oil pressure one day testing and found the crank had flexed hard enough to knock the oil pump loose. Had clearanced the pump to clear the crank during assembly. Caps had walked pretty hard. Changed the bearings and took some timing out. Put one piston in the lathe and opened up the ring grrove where it had pinched rings a bit.

Missed the race we were trying to get to.

Got it going again. It ran so hard almost blew it over testing. Killed another set of bearings. Missed another race. Caps walking pretty bad. Crank was not pretty Our friend and Shazam CC Mike Boyce said it has to be timing. Crap we are running methanol 9.4 compression and only have 33 degrees of timing. Called Brodix and they confirmed 31 degrees max with the Head Hunter heads.

Decision time. Wanting to get to the World Finals. Asked Info Jr. what does he want to do? All we have time to do is roll in another set of bearings and back the timing off. We decided to go for it. Make a few passes and check the oil filter. If it's good keep going, if it's ugly pack it up and bring it home in one piece

Set the timing to 27 degrees went to the WF made a couple really good passes. Checked the oil filter and it was ugly. :mad: Has to be an oiling issue.

Brought it home and didnt touch it all winter. Pulled the engine a couple of weeks ago. It had only killed the rear main bearing. Everything else looked great. As it turns out the rear main on the crank was not happy and the block line hone on the rear main was not either.

Analysis. Damaged it with too much timing. Did not have it apart the last time to find out the crank and block was not happy.

Just set the engine back in the boat yesterday. Ground the crank and line honed the block. Put a Titan oil pump on it. Thanks Steven Gearhead. New piston for the one we repaired. Should last all season this year. :shock:

Current challenge: getting control of the boost.

Couple pics of upgrades. Oil pump and bigger oil lines going to the Oberg filter. Moved the corner of the oil pan out to clear the pump. Very lucky it was so simple. Info Jr. getting the boat ready to drop it in.





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#106 ·
Kind of theb reverse of the guys with turbo T birds poking holes in the waste gate line:happy:
So is each one(or pair) a different spring pressure?

Personally, I would just change the pulley sizes. But then thats me:yes:



 
#107 ·
Wastegate changes do nothing. I'm not redesigning anything this year.

Gonna bleed off some boost and add some drag and hopefully get it close to the number.
 
#108 · (Edited)
Thats actually not a bad problem to have. There are plenty of ways to slow it down. Feed that driver some biscuits & gravy :D

On a serious note though, you want to rethink the idea of controlling boost by causing a boost leak (even though it works), It will allow those turbos to run away with themselves and over speed. Theres nothing to hold them back. When they do that they might stay together for a while but when they decide to explode they will send the exhaust turbin wheel (which will be spinning in excess of 150,000rpms) out of the pipe along with plenty of schapnel and might end up in a crowd of people. I have exploded one like that before , a small 55mm turbo , and let me tell you it was a scarry sob. The exhaust turbin tore up the turbin housing, tore a hole in the tail pipe on its way out and then sounded like a bullet from a 30-.06 on it way across the lake. Glad nobody was in the way of it. And that turbin wheel didnt weigh 1/2 what these ones do.
"If" you were going to do it that way , you could pick up a boost signal at your compressor housings were the boost is higher than what is actually in the intake ,and add another port to your BOV on the hat (to the opposite side of the diaphram) and allow the boost from the compressor to open the BOV and provide the leak. Then if you put a mini air pressure regulator in that line up were the driver could reach it , it would be adjustable. But as I've stated, theres a very good reason that the Pro's dont go at it from that direction. Be safe. Hass
 
#109 ·
Thanks Hass. We are only going to loose what I estimate 6 or 8 lbs of boost. Will still be plenty of load on the compressor. We can plow the water with the boat. Not do it all with engine.

And If they can't live for 8 seconds like that. Maybe we should put the 10-71 on it. :shock:
 
#112 ·
Wouldn't an AMD 500 or 1000 boost controller work?
No, at this point it will require a redesign of the turbo header and wastegate placement to gain total control over the boost. And that still might not get "total" control over it. Another route would be to introduce a very small amount of backpressure by adding some form of adjustable muffler after the turbo, maybe a set of the adjustable supertrap header muffs that the dirt track guys run. Would be cheap and easy to try.
 
#114 ·
The reason for the boost control problems is because these turbo header were designed for max power output and low backpressure in the header, which they do perfectly. When Mark made this vid the engine as in the boat had less backpressure in the header than the boost reading. 27 psi of boost and a lower amount of backpressure. When they put it on the dyno , adding those huge 8" flex pipes to expell the gases from the dyno cell caused enough backpressure in the header to divert more to the gates and his boost dropped to 10psi. He had to crank up the wastegates to get back to the 27psi of boost but was now at 44psi of backpressure in the header. Thats were it was run to make that 1809hp. Just imagine how much power that thing is making in actual use with 27psi of boost and less backpressure!
The moral of the story is that adding a little backpressure after the turbo will certainly gain some boost control. Its a bandaid fix, the correct fix is a well designed header designed for boost control but the header muff. idea will work too, and it is easily removable in the event you ever need to make some real power.
 
#116 ·
Why not just add a foot or more of tail pipe to the exhaust tips? Maybe they look a little goofy, but I'd think with some testing you could "tune" in the desired back pressure needed to control boost just enough to get the boost value you want out of this setup.

Saw a turbo straight six build running about 15lbs of boost gain almost 60hp by going from a 3inch with high flow muffler exhaust to a 4 inch without a muffler exhaust! A setup with not too many cubes (200ish) and not much boost and still a massive effect on power!...all because of exhaust back pressure as hass has mentioned.

Andrew
 
#118 · (Edited)
:idea: Now you're thinking!

A boost operated semi rain cap thingie, that gradually covers the exhaust in unison with (or even after) the waste gate opening. Go patent that shit Bob! Great idea.

 
#124 · (Edited)
Funny you should post that pic at this time for me.
I've been hanging around with this girl who was an electrician in the Air Force and worked on F15 fighters.
I was telling her about my boat which she thought was real cool.
I was talking up how fast it went and how hard it accellerated.
She said, "I rode in an F15 and we went Mach 2" (1450 mph)
Did THAT put things in perspective........:))eek:))
She had multiple levels of pilots liscenses and instrument flight rating at that time.

Then I was embarrassed to show her my boats wiring birds nest when she came over to my house.
 
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