Dula

Hello Everyone!

I am a rare poster but I today I am seeking help in the forums. I currently have a PTE 6262 on a built 2.0. Shortish mod list includes

Wiseco Assymetrical Pistons (not the high compression ones)
Wiseco boostline rods
Cosworth M3 cams (280 intake 272 exhaust)
AMS intake manifold
Boomba throttle body with all 3 inch piping
Mild ported head with Ferrea valvetrain
2150 injectors
Haltech Elite 2000
I have a forward facing kit (with an A/C kit that my tuner despises ... something about "street" cars should not have A/C but I don't like to sweat so its whatever)
V-band on both sides.

Currently the turbo is only making like 10 pounds of boost so we are like 95% sure that the compressor wheel is shot. In order to not spend a ton of extra money I am pretty sure I need to keep the turbo precision due to geometry purposes.

I don't do any dig racing and only roll racing (trying to keep the stock 6 speed alive). I still like to drive the car to work every now and then but like to keep the miles low (about 27k on the clock right now)

So from all this I have kinda narrowed down to either a 6466 or a 6870. I am undecided on the ar size (mainly because I don't fully understand them yet, still learning). At this power level I am trying to decide how much spool time I will have to give up especially due to the displacement but I felt that the 2.0 was the more balanced of the size options for what I was going with at the time.

Please if you require any more information to help me make my decision please feel free to ask. I am not totally opposed from moving away from precision but I don't necessarily see a reason currently.

Sorry for the long post, I am an Industrial Engineer and feel compelled to give comprehensive descriptions. Thank you in advanced!

MinusPrevious

iTrader: (3)

Hey, thanks for posting. Be great to get you to join the group on a regular basis

My setup is just beyond stock running an FP HTA71 setup. We do have some high level engine build members who can offer some meaningful opinions

Joe

ConEvo

In relation with those 2 turbos, 6466 is more street friendly. It spools prob around 400rpm sooner than 6870. The spool time depends on a/r, fuel (93 or e85) etc. Regarding a/r twinscroll tend to spool a bit qucker than single scroll. If you are on single scroll 0.82 would be fine, but if you are on twinscroll you should look into 1.00a/r or even 1.15. If you like would run it around 30psi I would say that 6466 is the best option between these two. If you run more than that and want a high hp 6870 will be better, especially on 9k territtory. Generally, it depends on want you like to achieve with your car, and what is the purpose of your setup. If you are thinking of other turbos also, although i am not familiar with Borg Warner, they seem to be the most transient turbo in the market. Also FP are known to be great. My suggestion to you, is to firstly decide what is your horsepower goal, what fuel you will use (which will also be relevant with the boost threshold) and after that pick the turbo which will get you there. Not the biggest one, but also not the smallest one. Not the biggest for huuuuge lag, and not the smallest to push it to the limits

Dula

Thank you! I will do my best... it is a nice break during the day to just get on here and read the forums. If I can do that then I should be able to contribute from time to time.

The car is now a dedicated e85 car. We were pushing high 30's ish psi (I do not run a boost gauge I just pray and trust into the Haltech). My manifold is a v-band so I am limited to a single scroll. For me I do not necessarily have a horsepower goal per se. The 6870 would get me into the 1000 hp range but at what cost? The 6466 would get me deep into the 800's and possibly 900's but we would be maxing the turbo out. I could achieve the same power out of the 6870 and not have the turbo as a limiting factor once again.

ConEvo

So it depends on what your ultimate goal is.6870 is more drag oriented and 6466 more street friendly. 30 high's psi would both turbos would work fine, but i think 6870 to shine more than 6466 would need to be around 40-45psi. high's 30 I think the results would be pretty similar. On e85 I think 850 or even 900whp is possible with an efficient setup and spot-on tune

LetsGetThisDone

iTrader: (1)

I would go with the 6466 since its a 2.0L, single scroll manifold, and a street car. With the mild head porting, and mild(ish) cams I would expect low 800's with boost in the high 30's to low 40's. I would go with the .82 A/R turbine housing. To make 900 with the 6466 you will need a fully ported head, and bigger cams (GSC S3's for example). But the 6466 at 800-850whp is very fun.

If you had a twin scroll manifold or this was a racecar, the 6870 would be worth a look, but (IMO) not on a vband manifold for the street.

Dula

Well fortunately we we hit that little 5% chance and found a couple of boost leaks and got them fixed. Regapped the plugs and made a little more power and broke 4th gear. Must have cracked the case somewhere because I have a huge puddle of fluid under the car. Tranny shopping time!

Thank you everyone for your input!

ConEvo

Aww that sucks. You have a 5speed or 6speed?

Dula

I had a 6 speed... just ordered a 5 speed

Pal215

iTrader: (12)

Sorry to hear about the broken 4th. If this was on the dyno with some rest between pulls, it was likely mechanical stress failure and not so much excess heat. Therefore an oil cooler system may not have helped here. I have learned from people on this forum and transmission shops, some that refuse to service the 6 speed now, that it takes a lot to get the 6 speed to survive long term under high hp. The fact that it lasted as long as it did under your power is actually impressive.

One of our best transmission builders measured the 6 speed gear set. Gears 1 - 3 are thicker than in the 5 speed and approximately the same size each. Gears 4 - 6 are thinner than in the 5 speed (6th being around the same size as 5th). One problem is that the shaft they all ride on flexes away slightly from the final drive gear set under hard torque. This is a normal problem with manual transmissions because you can't put an extra "through hole" bearing flange from the trans case to the mid section of the shaft further stabilize the shaft in the middle and keep it from pushing away. The smaller sump in the 6 speed keeps heat high on the track as well. Albins built a stronger 3,4,5 gear set that they tested to a reliable 500hp track driven. This would probably make it great for 600 to 700hp on the street. However, with your 800+ hp, the 6 speed never stood a chance in its OEM design. Have you thought about a sequential style transmission?

Dula

We are just doing street tuning and it was in the middle of a pull shifting from 3 to 4. I don't have a tranny cooler on it and never really wanted to waste the money trying to make it last. I also didn't see any point in replacing the transmission until something blew apart. The old adage of "if it ain't broke don't fix it"/

I have thought about going to a sequential but the bench seems pretty split on street drivability. It is a known fact that they will in fact wear down differently than a normal transmission and will be subjected to more wear when being used "street driving". Along those lines the cost to rebuild them is a lot higher than the cost to rebuild a 5 speed. For the time being I cannot cost justify going to a sequential transmission yet. I figure that after I have the 5 speed in the car I will see how this gear-set will hold up. I will be getting a brand new 3rd and 4th and a complete REM treatment on the gears and carbon syncros and a billet output tube. RRT Transmission Link.

I am very excited to see how this will turn out!

Pal215

iTrader: (12)

I hearya there. The 5 speed will treat you right and last a long time. Daily driving on 800+whp is too awesome.