Experiance with twins?...whats your opinion?

[oilandgasoutlaw]

Im finishing gathering things for my TT set up, and im looking for some opinions. I just purchased a custom TT kit. The kit is a bumper mount kit like the hellion kits, but its forward facing with THP headers. It came with twin billet wheel precision 67's. I know this is a little much turbo for what im shooting for now, but it will give me room and options down the road. They are T3 turbine housings with a/r of .63. I plan of running full exhaust with e-dumps off the down pipes. I will be running a mach1/cobra intake, stock 04 heads, with a stock displacement bottom end.

Couple of things I am curious of are, opinions of some cams I have vs stock ones (which I have also), and how you think the spool time will be. (I am running a T-56)


The cams are as follows:
Exhaust Valve Lift (in.)0.45Intake Valve Lift (in.)0.475RPM Range1000-7000Int. Duration @ .050 in. (Deg)230Int. Duration Advertised (Deg)230Exh. Duration @ .050 in. (Deg)232Exh. Duration Advertised (Deg)267.

Before anyone freaks out, these are a "blower" cam but they really dont seem like they would be to bad of a fit in the reading Ive done. I am looking for more bottom and mid power, but in the same if stock cams are not going to give me a significant advantage over these then im not wasting my time swapping them.

 

[Juiced46]

Spool is going to be greatly affected by how the cams are degreed in. What is your engine combo? Compression? Those 67s will be a bit much I think for what you will need. Spool is going to be super lazy with a stick. You are really leaving alot on the table and there really is no need for that size turbo. You will not have any bottom end- midrange power. My guess that setup is not going to full spool until around 5000rpms. Put smaller turbos on it. Degree the cams properly for quicker spool if you want the power to come on fast.

 

[1Fast-Turbo-Cou]

Spool is going to be greatly affected by how the cams are degreed in. What is your engine combo? Compression? Those 67s will be a bit much I think for what you will need. Spool is going to be super lazy with a stick. You are really leaving alot on the table and there really is no need for that size turbo. You will not have any bottom end- midrange power. My guess that setup is not going to full spool until around 5000rpms. Put smaller turbos on it. Degree the cams properly for quicker spool if you want the power to come on fast.

I agree. That's a ton of turbo.

 

[oilandgasoutlaw]

It's a stock displacement motor with JE pistons. I'm not exactly sure on the compression, I just picked the car about two months ago and am trying to track down previous owners to get more details. My numbers are really similar to stock compression guys so it close. I know they are big but it's what came with the kit. I was hoping with them being .63 t3 housings and billit wheel they would spool quick.

 

[tt335ci03cobra]

It'll be pretty laggy. I had twin 57/48's with .63 a/r's and they fully spoiled by 3500rpms on a stock terminator 4.6 longblock but it had a custom cold side and very cool 63* iat's.

I'd honestly sell the 67's and look for twin 60's at most. You can make 1000whp on twin 58's with a proper hot/cold side.

I'd recommend downsizing but you could hook em up, see how you like it, then consider down sizing at that point if it's too laggy for ya.

You'll need to tune it each time you change turbos though IMO for safe performance.

Good luck man, if you have additional question throw em out there so we can possibly help.

 

[tt335ci03cobra]

That seems a mild enough blower can but I'd run stockers if you still have em. Turbo modulars usually like a little more exhaust vs intake duration on an average. Don't quote me too hard on cam ideas though as I have an elementary understand of specing a cam. I'd consult a shop you trust.

 

[oilandgasoutlaw]

I definitely throw the stock cams back in, especially if it will effect my power range significantly. I'm really considering just sticking with the blower. At least I spent a ton of money to start having second thoughts. As far as the tuning goes when swapping around turbos, have pro-racer software so it's not a big deal. In the same though I can say I won't be happy with something that won't spool untill 5000 rpm.

 

[tt335ci03cobra]

Basically it would boil down to what your goals are with the car. Can you lay out what you're looking for performance/application/dd or weekend car, street or track, etc?

If you have everything except the turbos are too large, then sell the turbos and get something usable like twin 60's. I'm sure a set of usable turbos are for sale now or will be shortly. I sold my 57/48's which made 900whp for $750 with a custom dual in dual out intercooler included.

All things said, if you're not sure what exactly to spec up when going turbo, then it'll come down to doing the research to learn how to size and spec components (it's pretty easy, tons of info exists on turbo modulars, specifically stock long block 03/4 terminator mills) or deciding to stay blower and persue that route to hit your goals.

 

[Juiced46]

I definitely throw the stock cams back in, especially if it will effect my power range significantly. I'm really considering just sticking with the blower. At least I spent a ton of money to start having second thoughts. As far as the tuning goes when swapping around turbos, have pro-racer software so it's not a big deal. In the same though I can say I won't be happy with something that won't spool untill 5000 rpm.

I wouldn't get down and out so fast. Like mentioned. Just get a different set of turbos. Sell the 67s. I would look in the 57 to 62mm range max. The 67s are going to spool slow and you will hate the car and turn into one of those "I hated my turbo setup and went back to blower" guys. Don't do that. Just get the proper sized turbos and have fun! A pair of 57s will get you into the 800rwhp range and have superfast spool. If you want more go with some 61s or Billet 62s.

 

[oilandgasoutlaw]

The car is a toy for me. Only drive it on nice days when I feel like it. I would like to have 750 - 850 rwhp on the daily with the porental to make 1000+ eventually. In the same I want something that I can hop in and drive 300 miles to visit family and friends in the summer, and not worry about getting there. I have lots of experiance with lt/ls motors and N2O, but only limited turbo experiance. I am definitely still learning and I have done a ton of research. Why I made the post in the first place is I started doubting what I was told about spooling. Which was, the car would spool them 2-3k easily. I kind of bought in on thos since they have t3 hotsides with a/r of .63. Reading more into it i started rwally wondering, especially since I'm running a T-56. I do want somthing that will do well ripping around town too, and not just be a freeway monster.

I'm not getting down about it because it's "to much", or to complicated. There's really two parts to the reconsidering. First I really don't want to hack up this car. It only has 22k on it and I just feel like If I follow through with this route I'd be better suited to find a GT or Mach 1 to do surgery on, and throw and auto in it. Now this is just a thought and really the lesser of the woes currently.

The bigger issue is there are going to be some lay offs at work in the coming months. I'm a contract employee in the oil and gas industry, and it's just part of the gig. I don't know if I'll be one of the guys that gets released but I'm pretty conservitive financilly, so I am a little hesitant to start this project. I still have quite a few parts to purchase to support the turbos and get the car to where I want it to be . Basically I don't want to dump another 6k + into it right this second, and I'm not niave about what it costs to do one of these set ups the "right" way. Part of me feels like if I sold the twin set up I could use that money and snatch up a pair of ported heads ,go return style on my fuel system., get some ID1000's,.....you get the point. I could still make progress that would benifit me no matter where the boost is coming from, weather it's a turbo or blower. When I first started this undertaking I was prepared to shell out the money to do everything at once, but with knowing that we are going to slow down I just can't bring my self to it right now.

I don't have to make a decision today, or tomorrow. Bur whend I do make a decision I don't want to look back and think " why did I do that?".

 

[oilandgasoutlaw]

So a little more info on the turbos before I commit one way or another...

They are 6765sp turbos.
Compressor is 2.655 ind /3.477 exd
ported s housing for compressor with a .70 ar
Turbine is 2.92 ind / 2.542 exd - 76 trim
T3 housing with .82 ar on exhaust. ( I was told they were .63 housings but when I looked they are stamped .82)

So turbo gurus please chime in and let me know what you think....

 

[Nightmare302]

So a little more info on the turbos before I commit one way or another...

They are 6765sp turbos.
Compressor is 2.655 ind /3.477 exd
ported s housing for compressor with a .70 ar
Turbine is 2.92 ind / 2.542 exd - 76 trim
T3 housing with .82 ar on exhaust. ( I was told they were .63 housings but when I looked they are stamped .82)

So turbo gurus please chime in and let me know what you think....

If you want street manners those are not the turbo's for you. Even with the T3 flange they will be laggy on a low compression 281. They will make great power and come on strong but with what you said you need smaller turbo with smaller exhaust housings they would probably spool around 4k. If you want to make more than 1krwhp I'd look for someone wanting to step up that has the 6262 precisions. Either way, to meet the 1krwhp you are going to have some type of lag in a stick car. Expect if you get the correct spec for the car to come on around 3500-4000rpm. The 6262's can support 1krwhp through a stick pretty easy.

 

[tt335ci03cobra]

Ok, thanks for all the info!

Very attainable goals with healthy twin 58's on e85, for pump gas, twin 58's will hit 750whp with a healthy stage 2 cam, or a nicely done custom kit. On say a factory hp racing kit, 58's should make about 700-725whp@15psi if my memory/guestimations are on point.

1000+whp may need more than 58's on a stock long block, but if you have a great supporting cast like a true 3" hotside, the forward facing headers as you mentioned, a well sorted intercooler and cold side, and good tuning, I believe 1000-1050hp or so could be possible around 28psi on healthy twin 58's but you will be experiencing back pressure at that point as the t3 housings will literally be maxed out IMO.

I think you have an excellent idea to sell these turbos you have, and use the money on fuel, spark, etc. Buy dualy usable components like those, and you will be doing a very smart thing.

I'd go twins, but that's because I have a comfortable understanding of them. You can likely make the same numbers with a 4.0 twin screw, maybe even a 3.6 but I'm not as versed on the twin screw game anymore. I do fully believe it'll be less expensive, and still very reliable to go twin screw.

With a twin screw, I'd imagine you'd need a healthy head and cam combo plus about 30-33psi to make 1,000whp with a 3.6, or about 28-30psi on a 4.0 but again I really am not versed on them.

 

[Nightmare302]

Quoting PSI is silly since it's only a measure of restriction and hundreds of variables come into play when speaking of psi. Simply put, a turbo will out perform a twin screw and be easier on the motor (specially the crank) BUT you don't have to deal with lag. If I could have any setup on my car I'd have a 9.5:1 compression car with a cleaned up intake and heads with custom baby cams to help spool with twin 6262's on E85 and a TH400. That car would haul the mail and wouldn't be "that" wild and perfectly streetable.

 

[tt335ci03cobra]

Yes, that is true that boost is as you describe. I think many of us know how velocity, volume and psi relate and more so don't relate to one another... Just saying what people with stock long block terminators have hit. The op has hp goals and it's helpful to have a general guideline of what power adder and boost settings usually makes what power level and to what degree your having to max out the given power adders.

Only other way to discuss plausible hp without discussing boost settings for a particular power adder combo would be to break it down into necistated air flow for power production via volumetric efficiency dependant calculations with a plausible window of error...

I think that would be sillier than stating numbers that other stock long block 03 cobras have made. One approach would be theory and the other would be duplication... It's a 10 year old power train and just about every type of build has been done on a terminator longblock. Why go back to the chalk board and perform theoretical maths when the books already written with the answers in the back?

It's just some info to help the op out with decision making. It'd be silly to try to rewrite the book this late in the game.

As an Aside, none of those numbers work at my altitude because I'm 4600ft above sea level, and honestly up here it's much more advantageous to go turbo for high hp builds. Cooling and airflow (oxygen I should say) related needs all pretty much mandate hitting the chalk board and figuring out how to combat the 12-14% sparser air as well.

To the op, what altitude and humidity do you experience during driving seasons with the cobra?

 

[oilandgasoutlaw]

Sounds good thanks for the info. Think I'm gonna stick with the KB for the cobra, since it's a put around on nice Sundays car. Going to dedicate the turbo set up to a project that will be primarily track use.

 

[Turbo98]

From what I've experienced, the two main factors in determining spool (besides the turbos) are the intake manifold runner length and the cams. The intake you have is suited for broad midrange power up to 7K. The blower cams will kill your midrange driveability-no doubt. It will be a mis-match with the intake. Yes, the turbos are huge but if you're set on using them because you have them, throw the stock cams in and I don't think your spool will be toooooo bad. BTW, I had 5857 turbos and made over 1000rwhp and that was with the old cast-wheel Precisions. With their new wheel designs, it would be a piece of cake. Then with stock cams and that intake, they would light up very fast and it would be a fun car to drive.

 

[oilandgasoutlaw]

I'm in pa and it's a summer car so altitude is usually 800 to 2500 ft. Humidity is usually pretty high. 80-90%.