I'm going to run 2 Holset HX55 or H2D's, there off diesel trucks, there cheap, and made very well. Just thought I would add.
it gets to desired max boost(4psi) almost instantly about 1/2 way to 60 foot then the boost slowly creeps up by 1/8 mile it gets to 8psi by 1/4 it gets to 12psi. as far as 6000 it does not feel like power is running out at all. before turbos, motor reved slowly, with turbos it revs faster than any small block ive ever drove that includes a 2005 z06 6 speed corvette. if it is letting up i cant feel it. but i normally shift at 5000-5200 on street legal night and on bracket class 8.20(1/8) i sift at 3200 and pull the timing down to 2deg and still run 8.15 if the air is right otherwise it will run 8.25. by the way i beat the z06 by about 3 cars on street leagal nights(heads up) he hates my car.
there is i guy running one of those big disel turbo's on his trans am 455. do you think that 2 might be to much. just curious http://www.highperformancepontiac.com/tech/0309pon_1979_turbo_trans_am/index.html
Wow...4 psi setpoint to 12psi...that's some creep! Usually you think about it on the order of 1-2 psi. You pull the timing down to 2* BTDC? Wow. I have to pull the timing back to ~12-13 on a hot day on my 94 V6 with the 10psi I'm running and 9:1 compression. But I could understand that with 12psi on a 9.5:1 motor. Wow.... Do you have any idea of your air/fuel ratio at those levels? Must be pretty rich if it's surviving. :3gears: If you can't control the boost any more than that I would definitely think it's the size of the wastegates and/or turbine housing size. That V6 of mine has a 0.8 A/R turbine housing that is actually a T3 housing but the turbine wheel is a P-trim T4, and it's a 204in^3. So double that and it's only 408in^3...still a good bit lower than a 455in^3 if you put two of them on it. The V6 doesn't spool super quick, but it does pretty good. I bet your exhaust backpressures are pretty dang high. What size wastegates are you running? Are they internal or external? I would think 38mm externals would be a good size.
i'm not sure on the size i think 35mm external each side ill have to check and get back to you. but thats not all, the shop that built the turbo headers used 1 3/8 primary tubes. He said that was to keep the turbo lag down. but in my opinion the tubes should have been 1 7/8" - 2" regardless of turbo lag. I think that this is also a source of my boost creep. Ill tell you what, if i had to do it over i would have done things a lot different. I do value your input a lot. it has helped to confirm a lot of what i thought.
1 3/8" sounds too small. Mine are 1 3/4" and the boost came up very quick with .69 a/r housings. After I changed to a tighter converter it wouldn't control the boost until I changed to Turbonetics race gates. Take the wastegates off and see if you can still build boost! I know it sounds silly but I've heard of the exhaust velocity being so high that it would do that. If it makes boost with the wastegates removed, you'll need to do something other than just changing to larger wastegates.
i took the springs out of the wast gates and yes it still built boost it took all the way to the end of the track but it still reached 9 psi. that is why I said it should be 1 7/8"-2". I know it is not because turbos are to big because i also took one turbo out of the loop and the car actually lost power in 3rd gear and started slowing down. did you make your own headers.
The racegate is a 1.625"/42mm wastegate? That should help quite a bit. By tighter converter do you mean one with a higher stall? So the RPM comes up faster? I'm a bit new to turbos and autos... I know a guy with a 427 LSX that he just built up for a 4th gen trans am. He's running two T70s with a 0.68 A/R turbine housing and two 38mm wastegates. He ran the same setup on his 350 LS1. He says he's starting to run out of turbo at 1090 wheel hp and 19psi, 109 race gas. So that's a comparison point on displacement anyway.
Was the boost with the one turbo still above the set point? I'm assuming the springs in the wastegates are 4psi springs? I believe you'd lose power, getting half the flow. But did it still overboost? I still think a T3 turbine may be a bit small especially with a 0.5 a/r housing. A T3 turbine with a 0.5 a/r housing still flows less than a T4 turbine with a 0.5 a/r ratio. So just comparing a/r ratios across different turbines isn't a fair comparison.
Yep. I couldn't find anyone at the time who could tell me what size tubing to use so I guessimated 1 3/4" should work. It's not a bad size and I almost wonder if 2" would be too much unless the primaries were really short. Lower stall. It loaded the engine more at a lower RPM.
Ah, ok. Yea, I think if you get too big with the primaries then you really start to lose exhaust gas velocity/pressure.
I had said earlier that it had 1 3/8 primary tubes i measured them today and they are actually 1 1/2 OD i still think that is to small what do you think.
I just measured an exhaust gasket port, and the area is 2.184 inches. The area of a 1 1/2" dia tube is 1.485 (that's assuming it's 1 1/2" on the outside with a .0625 wall). 1 5/8" tube area is 1.767" 1 3/4" tube area is 2.074" 1 7/8" tube area is 2.405" As far as the tube size goes, I may need to back up a couple of steps. Here's a quote from another board concerning header tube size and HP numbers: Depending on how fast you want to go, you may be better off to spend your money in other areas before upgrading to a larger tube size.
Do you think it matters what kind of things you have after the headers? It sounds like from that quote that they're talking about naturally aspirated engines. Possibly race setups without mufflers? If you had some larger exhaust restrictions down-stream of the headers would you want some larger primaries to act as a kind of buffer? Or am I just making things up? ou: I'm not sure how this would come into play with a turbo setup though. I just know that you want to balance between turbine inlet pressure and reversion. If you have a high pressure drop accross the turbine velocities should be high and you should get a good spool rate. This means high pressure between the engine and turbocharger, and lower pressure(free flowing tailpipe and mufflers) after the turbo. But the bad thing about high turbine inlet pressure is it means high backpressure on the exhaust valve and if you have a cam with overlap you'll get reversion, or at least not as good exhaust purge and the intake charge will become a little inert making combustion not as good.
Nope, that's with turbos. I was suprised that so much power could be made with small primary tubes, but that's good news!
This might sound really crazy, but if it were me, I'd buy a rusty 10-15 year old school bus with a 5.9 cummins diesel and an Allison 545 auto trans for $1800 and swap that drivetrain into your tow rig. The allison/cummins combo is 100% bullitproof, will last 1/2 a million miles, and give better MPG than your stock 454. Also, you can EASILY crank a diesel up to un-real HP levels for just a few bucks. After the swap, Ebay off the 454, a few of the school bus pieces, and send the carcus to the scrap-pile, and you could actually turn a profit on the venture! As a bonus, you could then run the diesel on free fuel!!! See here: www.frybrid.com
Ok...yet another revision of the turbo/engine calculator. This one includes a table based on rpm that has things like: turbo air requirements, fuel injector size, and if you enter the fuel rail pressure higher than standard you can see what injector size you can buy and run at that pressure to get enough fuel. Again, save/download as .xls instead of .txt.
Well I'm one step closer to TT Buickness. I picked up a couple of used turbos and wastegates from a guy who needs to upgrade for his 427 LSx to bigger ones. Alan, would you mind letting us know your compression ratio on that 455? How much boost and ignition timing? I'm thinking about trying these on my stock rebuild 430 with a SPX manifold converted to EFI. Since the stock compression ratio of this '69 430 is 10.25 I'm going to have to be pretty moderate on the boost with 93 octane. I pretty much just need to start fabricating(starting with the intake). Anyone want to estimate what kind of power I'd make? As for the throttle body, I'm thinking about building something simular to this: http://www.intakeelbows.com/universal.htm The turbos are two MasterPower T-70's with a P-trim T4 turbine and 0.68 A/R ratio. Wastegates are two 38mm Tials. http://www.turbocamaroproject.com/TT430/TT430.html
Check out http://www.turbofast.com.au/TFmatch.html it shows that with 10.25 comp you will only be able to run 3-4 psi with a 75 VE and you should make 500HP That is unless you are going to Intercool or alcohol inject then of course you would be able to run moor boost
I agree I should heed caution, but it looks like that calculator has a pretty big safety factor built into it. I entered my specs on that turbocharged V6 camaro I have with 9:1 compression and running 10psi boost and 85% VE and it tells me I need to be running 102.8 octane. I've only run 93 in it and while I have to tune the ignition down to near 13 BTDC it does run well and has been for several years. Even your combination: 4.313/3.9 (assuming stock bore), 9.5:1, 85VE, and you've said as much as 12psi boost when it creeps: 107.8 octane. While I do agree high static compression and turbos don't mix, I think it's worth a cautious try. Does anyone happen to have a good feel for stock 430 volumetric efficiencies with stock heads/cam? Eventually if I want to see some real numbers I'll have to have a nice built 455(with girdle) and at that time I could have some lower compression built in. It would also match the Stg 2 SEs a little better as well.
