Question I'm building a twin turbo LT1 and I have a Z06 MAF and a 411 LSx pcm with EFI Connections 24x ignition will I have any issues with this setup at 15#-18# of boost?

 

My new setup is a fully machined and blueprinted 383 LT1 with splayed billet main caps, Howards Tracksmart 4340 forged crank, 6" Howards 4340 forged rods w ARP 2000 bolts, Mahle forged ft pistons 10.3:1 scr, AFR comp 210 heads, GMPP 847 cam 234*/242* .575"/.575" 112 lsa cam, Edelbrock Victor EFI intake, Accufab 4150 sytle tb, Canton oilpan, Ebay twin turbo headers modded for T4 flange, Treadstone fmic, Turbonetics twin 62-1 .96 a/r p trim turbos, Z06 maf (may go sd and leave this out), EFI Connections 24x LSx coil per cylinder ignition with LSx 411 pcm and my car also has a built T56 trans and 4.10 gears. This is as far as I've gotten so far, still need to figure out injector size whether or not to use the MAF etc. so any advice or info would be great. I do have questions about how exhaust a/r size affects spool up time, how to determine what size wg and springs to use and what size bov as well and are any of you guys using electronic boost controllers?

 

usually by changing the ar of the turbine housing usually makes the boost come in later or sooner about 200rpm for a ball park

 

Thanks M&M I've been reading about some of the twin turbo build here and most seem to run .68 a/r exhaust housings and mine are .96 a/r do I have them sized correctly? I don't need instant boost as it would only blow the tires off with the 4.30 gears I have. My thinking is with the cubes +m6+gears= less stress on the clutch, trans and rear so I geared the car to run the 1/4 mile and in 6th gear I'll have a 2.15 final drive for cruising and long trips. I'm hoping what I'll get is a car that pulls really hard once the car is moving and the gears+cubes will get the car to launch at the track. My goal is 750 to 800 rwhp do you think I can get there with the current turbos or do I need something bigger and I intend to stay twin turbo regardless?

 

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above are some pics of t4 Ptrim exhaust housings from Lt. to Rt. .96,,.81,,.68

http://www.turbodriven.com//perform...wts=400&pt6_wd=83&pt6_wd2=74&pt6_wrsin=92044&

above is a link to the borgwarner match bot ,,watch the videos at the bottom and play with the numbers a little,,, looks like the 62mm or the 67mm plot up nicw on the compressor map

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Thanks again M&M that was very informative looks like I should be ok with the turbos I have.

 

I would say 1st, (and probably 2nd) gear are gonna be a waste with those rear gears.......I would think 3.50~3.55 would be as high (numerically) as you would EVER need to run with that combo.

 

Thanks Rickracer I know that bucks conventional wisdom but my turbos are sized for mid to upper end boost and power and I understand by my car being a manual trans (t56 6 spd) using higher gears will load the engine and therefore the turbos sooner but it will also put more stress on the clutch, input shaft of the trans and rear gears. Using the gears I have will allow the car to get moving off the line before the boost really kicks in giving it a better chance of hooking rather than blowing the tires off. Plus I can get the 3.54's later if my car doesn't work the way I'm thinking it will plus the car is a street/strip full weight car so crusing around out of boost the car will get up and go without having to downshift.

 

I tried high gears with turbo, it sucks. Your RPM will rise much faster than the turbo spools, it's kinda lame having those turbos and not being able to use them until 3rd gear

You'll end up doing as I did: try it, hate it and change gears.

 

Thanks Guillaume what size gears did you have in your IMPY SS and I assume you're an auto where my car is a manual also I can always buy another set of gears unfortunetly I have an S60 (Dana 60) rear in my car so the lowest gear I can get is a 3.54 which I may do and have them on hand. Also what were the trans ratio's in your trans when you had the steep gears, doesn't the 4l60e have a 3.05 first gear? My trans has a 2.66, 1.90, 1.57, 1.0, .74, .5 which I think will make all of the difference, but we'll see come spring, but thanks for the info and perspective. Hey what size is your engine and at what rpm do you reach full boost and how much boost are you running? Are you still using the MAF or did you go speed density, sorry for all of the questions just trying to get as much good info from people who are actually running similar setups.

 

I had 4.10 gears with 3.06 first (4L60e) and 28" tires. 1st gear was useless at the track.

I now have 3.23 gears and a 2.48 first gear (TH400). They feel just right and it drives really nice on the street because of the tight converter and small cam (Comp XFI grind, 224/224 and 113* LSA). I still have the stock stroke.
I leave on the transbrake @ roughly 3400 rpm and shift right before hitting 6000 rpm. It doesnt make power at/past that point, my stock heads are probably a big restriction at this point.

I am running a FAST classic EFI system in speed density and bank-to-bank injection. I use the optical sensor in the optispark as a cam sensor and the LTCC box to control the LS2 coils.
Boost is at 15-16 psi.

 

There is a Dana 61 that has a 3.07 and you can machine it to make it fit in the Dana 60 with positraction, a shop here in Mexico did it for my Ram Charger and now i have a 60 mph first gear lol

Here is some info from wikipedia

A variation of the Dana 60 known as a Dana 61 was made to accommodate gear ratios that allowed for better fuel mileage This was done as a direct result of the 1973 oil crisis. A 3.07:1 gear ratio was common for these axles and unachievable n a regular Dana 60. To allow for the different gearing, the Dana 61 had a greater pinion offset. This offset meant that a different carrier and a different ring and pinion had to be used. The Dana 6 was made in semi-float and full-float axles for select 4×2 Ford ¾-ton and 1 Ton Pickups and Vans from 1974 to 1987. A Dana 61 front axle was selectively used in Dodge 4×4 ¾-ton and 1 Ton pickups from 1987 to 1993. Although 3.00:1 and 3.07: gear sets are possible from a Dana 61 ower gear sets (4.56:1 on down) are not

 

Thanks for all the info guys, like I said I'll go ahead and get the Motive 3.54 gears after I get everything else up and running. Are there tuning issues when using the MAF, I notice lots of guys switch over to speed density when going boost? I have the EFI Connections 24x kit, 0411 pcm, HP Tuner Pro and I'm going to have Frost tune the car, I have the Z06 maf and I'd really like to use it if possible. I plan to run 15# - 20# of boost is that going to be a problem?

 

Well my build is under way I took my newly built engine back to the machine shop as I've sold my LE3 heads and will be ordering my AFR eliminator heads and hydra-rev kit next week and I'm also changing to the Jardine upswept forward headers as the ebay ones won't clear the accessory drive and ps pump. Jardine is building 4th gen fbody turbo headers for both LT1 and LS1 but they won't be available until end of March so these should fit with no problems.

 

AFR heads and hydra-rev kit ordered and I'm going to get the Jardine upswept and forward turbo headers as the ebay ones won't clear my ps pump and altenator, I'm also going with the Comp Turbo 6767s with the billet compressor wheels. What size injectors do do I need and what size fuel lines for 1000-1200 rwhp?
Also the sale fell through on my new LE3 LT1 heads so if anyone needs a set let me know.

 

Ordered my Jardine 1 3/4" stainless turbo headers and my Treadstone A2A intercooler, man I can't wait.

 

This thread needs more pictures!!!

 

Well I just ordered my Comp Turbo CT4-6767s with billet compressor wheels and journal bearings and my headers are being built and I should have them and my AFRs next week. Once the parts arrive I will post pics, here are some pics of my combo before the new parts. #ad
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Well my AFR 210s and Hydra-rev kit showed up last Thursday and I dropped them off at the machineshop. I spoke with Jardine and they shipped my 1 3/4" turbo headers on Monday so I should have them by early next week and my turbos should be shipped on 4/25/13.

 

Why are you opposed to going speed density? Also, I'm with everybody else on the gears, you're going to hate them.