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turbo build. Posted By: 12_bolt On: 06-05-2009 @ 21:00:54 Reply | Edit Hey guys, I am building a turbo lt1 and I am looking to make around 550+ hp to the wheels. I was thinking a stock motor with forged internals and 4 bolt main. and alot of boost has this been done before ? -- 2008 Yamaha R6S 1997 Trans Am - Fresh 357 LT1, Ported Heads W/ 1.6RR's and CC Springs, Comp Cams "Extreme" LT1 Camshaft, 224 / 236, lpp long tube headers, magnaflow cat back, 2600 Stall, 4.11's and some bling! Posted By: jjdynomite 
On:
06-05-2009 @ 21:31:38 Reply | Top | Edit
Talk to realquick check out his site @ lt1boost.net -- lsxltx.com Posted By: ROSST On: 06-06-2009 @ 07:46:05 Reply | Top | Edit 1 bar of boost or as us Americans say 14.7psi. will produce a lot more than 550 at the wheels. When you say a lot of boost you need to know what you are talking about. You want a very fast/scary HP motor, use the short block assmy. you mentioned. Use a 68 - 72 mm turbo (single) with .7 bar or about 9 psi. Make sure you deal with somebody who can do the combustion chambers correctly to get the compression ratio down to 7.0:1 Do not use a dished piston. Make the "bang" in the chamber not in the hole. use Cometic head gaskets, tell them what you are doing and they will make you a 3 layer set. No need to O-ring the heads. You also should use splayed 4 bolt caps with a stud kit not bolts. use stock cam, and and manifold no need for exspensive stuff, AFR 180cfm heads or better for sure. 58mm t-body at least. Depending on the amount of boost you think is a lot or you accually run, there will be other very important factors to consider and address. The 2 that are most importatnt are fuel delivery and how you manage it. Which in detail is pump flow, fuel line size, injector size which are all determined by the amount of boost you run. Lastly, the factory ECU only makes adjustments every 750 rpm in pulse width and timing movements, and will only use high impedance injectors. You may need low impedance injectors to feed enough fuel to the motor, I think the cut off point is 550 cc (i cant remember) which means you'll need an engine management sysytem. I personally dont think any of the US made ones are very good. Not even F.A.S.T. so you'll need one more than like if you run too much boost. any of the European are VERY good. such as Pie, Motech, DTA. They are all much better systems. They also run off of dos which means that you dont lose any data when you get a new version of Windows which is what the US systems are based off of. Do you have a thick wallet or know what you are getting into completely.? keep it mild and simple or you cross over and spend a LOT of money. keep it under 10 psi and you should be ok. At 7-9 psi.. you'll make (im not going to do the math right now) but over 650HP for sure. Fell free to contact me anytime if you have more Q's. I'll be happy to help. Ive been doing turbos for ..well say a long time. early 80's anyway. Ross. RT PERFORMANCE [ Edited on 06/06/2009 @ 07:49:15 ] Posted By: 12_bolt On: 06-06-2009 @ 14:33:41 Reply | Top | Edit WoW thanks you for the help! I am going to start on this build soon and im sure all have more questions. So you are saying with a stock forged motor at 10 psi i should be at 650hp ? -- 2008 Yamaha R6S 1997 Trans Am - Fresh 357 LT1, Ported Heads W/ 1.6RR's and CC Springs, Comp Cams "Extreme" LT1 Camshaft, 224 / 236, lpp long tube headers, magnaflow cat back, 2600 Stall, 4.11's and some bling! Posted By: ROSST On: 06-06-2009 @ 18:37:27 Reply | Top | Edit I would say yes. That bottom end has to be VERY strong. Dont cut corners there at all. I would look at Arrows or Carrillo Rods, something that good at least. JE pistons with a minimum of .250 dome thickness. Up to 10 - 12 psi you may be able to use a re-programmed ECU. I also wouldnt run more than 18 degrees total advance. Esp. with 93 oct. gas. maybe back it off to 16. If you plan on using this on the street and drive it often, get some toluene and add 22% to the fuel if you want to run as much as 12 psi. If you will keep it under 10 psi, you can get away with a 68mm turbo. anymore boost than that and you'll need something larger. These are not dead on facts but close. you'll have to follow up on a lot of this and verify/check to make sure. [ Edited on 06/06/2009 @ 18:39:45 ] Posted By: 95ttoplt1 On: 06-11-2009 @ 11:47:25 Reply | Top | Edit How are you running the OBD2 computer with boost? Just curious as I'm not sure how I would do it with an OBD1, unless I was going to use a FMU. I think I would just build a MegaSquirt. --  Posted By: ROSST On: 06-11-2009 @ 22:42:52 Reply | Top | Edit Are you asking me? I'm not running one at all. If you are asking how you could do it. I would say using a regulator that is vacume adjustable, IE: as MAP goes up so does fuel psi. and have the ECU tuned for longer pulse width to the injectors. With a larger injector it should be able to be tuned fairly simple. If in fact it can be made to feed higher boost levels then you would more than likely have to change over to a stand alone. Definaely get rid of the mass air flow sensor. and just run a MAP sensor. Posted By: Airbornec507 On: 06-11-2009 @ 23:13:19 Reply | Top | Edit You can run higher boost on our LT1 motors with stock PCM if you buy a two or three bar map, depending on the amount of boost you plan to push, then tune the PCM to operate in Speed Density mode only. Using a 2 bar map you can tune the SD tables as required. I created an excel spreadsheet that will do this if you have a wideband sensor and want to tune yourself. My spreadsheet is based off of a stock 1 bar sensor now. if you ruduce the resultant values by 50% and use a 2 bar sensor it will work in boosted applications. Not sure as to how much boost it will work with until you have to go to a 3 bar sensor and ruduce the resultant values by 33.33333% based off of the stock values then tune from there. I do know that if you plan on pushing over 100Kpa you need a 2 bar MAP sensor. Yes I have the Excel spreadsheet complete for the 1 bar and no I don't plan on spending another 4 hours to make up the two or three bar speadsheet. I'm sure it would be much quicker though since I have the base sheet to work off of completed. Point of the story is that you can run boost on the LT1 PCM without running an aftermarket FMU system. It's been done before but if you have the cash would probably be easier if you just go aftermarket as suggested. -- 
95 383 Z28 w/CC306, P&P Heads(272cfm), EPortworks Ported Intake, 3600 VIG Stall, CPT Pro Race 4L60E, Moser 12 bolt, 1.601 60'(W/3200 Stall) Posted By: ROSST On: 06-12-2009 @ 09:18:34 Reply | Top | Edit Airborne, you would probably know the answer to this, based on your knowlage of the factory ECU. Having the need to use more than a 1 bar map sensor, he would more than likely based on fuel demand end up with low impedance injectors anyway. Wouldnt he? So it may be safe to say that a factory ECU is limited to 1 bar of boost and maybe not even that much. Again, This is a math equation that would take me a few minutes to figure out and it is early in the morning. I'm still working on my 2nd coffee. Posted By: 95ttoplt1 On: 06-12-2009 @ 10:57:21 Reply | Top | Edit Makes sense Iz. You running a turbo now? BTW I am at Campbell now. We might have to meet up in north AL for a run sometime. -- Posted By: Airbornec507 On: 06-12-2009 @ 13:53:32 Reply | Top | Edit No not running a turbo but have thought about it since I have -16cc pistons. The reason I did the SD table was because my MAF seems to be fubar thus I'm tuning using the SD mode and the WOT tables. To create this excel spreadsheet I had to delve into the world of boosted applications to understand the concept of SD and how it works and can be manipulated. My spreadsheet is based off of VEmaster. Thus it's really nothing new just something made to work with any wideband that you can derive rpm and MAP from. ROSST: You can run low impedance injectors with a special adapter however there are folks that use the method listed above with high impedance inj. around #95 when running high boost and tune using the three bar MAP. Most folks do go to a dyno to get this done. I would only use the software that I have for small tweaks but not base tunes on a new set up. Posted By: ROSST On: 06-13-2009 @ 20:46:48 Reply | Top | Edit I believe high impedance injectors only go to 550cc. At 600cc's they are low imp. I didnt know that there is stuff out now to adapt the high to low for the factory stuff. I mainly use Motech, or DTA systems in my applicaions. I also dont use mass air flow sensors. In boosted appls there is no need for one with a stand along system. I also dont tune using a/f ratios. At 2 bar or more that can get you into trouble real fast. Wouldn't the injector drivers duty cycle double by cutting the impedance... ? Posted By: saoco383 On: 06-23-2009 @ 14:35:10 Reply | Top | Edit nice Posted By: 87bandit On: 06-25-2009 @ 20:51:36 Reply | Top | Edit stock rods/crank with upgraded bolts should be fine for 550hp just make sure you have a decent forged piston ontop 2 bolt main shouldnt be a problem either --  1994 Trans Am GT A4 - NOS Dry Kit, CC503, Comp 1.6 Magnum Rockers, K&N FIPK CAI, Trick Flow Elbow, 58mm TB, TP Built 4L60e, 3000 Stall, B&M Tranny Cooler, Pacesetter Midlength Headers, !EGR, !CAT, Cutout, Magnaflow Catback, M/T ET Streets, 30# SVO Injectors, Walbro 255lph, NGK TR6 Plugs, MSD 8.5mm Wires, Hypertech 160 Thermo, Manual Fan Switch, TB Bypass, LT4 KM, MAF Descreen, !Front Sway Bar, BMR Rear LCAs, MAC SFCs, Comp Engineering 3-way Adjustable Shocks, Energy Suspension Polyurethane Trans Mount, 3.73 gears Best Time: 7.56 @ 91.14mph (stock cam, stock tune, shitty tires) [ Edited on 06/25/2009 @ 20:51:56 ] Posted By: ROSST On: 06-29-2009 @ 21:52:18 Reply | Top | Edit I would dis-agree very much. You have to remember it is not RPM related that takes the toll on the block and rods in a turbo charged app. The crank acceleration when the boost comes in is something most engine builders have no concept of when it takes place. We are not talking about a motor that will spin 8500 with a compressin ratio of 13:1, it is a completely different animal. I have seen good 4bolt blocks have the crank "pushed" right out of the bottom of the block. During boost it will take a rod the strech it in two. Litterally pull it apart, from piston acceleration. 8psi and up..use a 4 bolt block and very good rods. 10 psi or more it is a must. You can diagree with me, but have somebody follow you with a wheel barrel to pick up the pieces, and some speedy dry to soak up the oil.
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