: Twin COMP 5858's for rear-mount build



lilgCTS-V
04-09-13, 11:41 AM
I've been wanting to do a twin turbo build for some time now and i've done just about all the research i could do, the only thing i really need help with is choosing the right turbo chargers. I thought about doing some CX racing GT35 turbo's because they seem to work but i feel going with a quality turbo will yield a better result. I was thinking of OIL-LESS COMP 5858 ball bearing turbo's, any expert opinions would be great !

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http://www.compturbo.com/products/ct2billet/ct2_5858

runsfromdacops
04-09-13, 12:02 PM
I have pte billet 5858s with S cover and v-band .82 ex housings on my rear mount setup.

Seems to be a geat combo for my car.

lilgCTS-V
04-09-13, 12:03 PM
What are you spooling at ?

VincentT
04-09-13, 06:22 PM
Kinda depends on your goals, but for the amount of boost that stock heads can handle, 5858's are right in line with what I've researched.

Edit: Not having compressor maps to look at makes this kind of stuff hard.

madramper
04-09-13, 10:59 PM
I went with www.workturbochargers.com. Give him a call and he will build you exactly what you need. He takes the guess work and worry out of the large purchase. I wound up with a pair that I never would have considered on my own. He said I should have boost by 2200 rpms and they are good for 1000hp.

runsfromdacops
04-10-13, 05:05 PM
Kinda depends on your goals, but for the amount of boost that stock heads can handle, 5858's are right in line with what I've researched.

Edit: Not having compressor maps to look at makes this kind of stuff hard.

Well im making 876/860 on a 383 and not running out of turbo yet. I think they are a little on the big side for a stock motor.I think they are going to give up right at 1kwhp

robojesus
04-10-13, 06:17 PM
wow, you're only able to make 1,000 rear wheel with your rear mounts... it must be hard being you.

(consider me thoroughly jealous)

HAMSTAR
04-10-13, 07:26 PM
Why isn't anyone here considering a single, smaller turbocharger that could net a yield like a maggie?

RyRidesMotoX
04-10-13, 08:19 PM
Why isn't anyone here considering a single, smaller turbocharger that could net a yield like a maggie?

A turbo is like a hooker.... Why have one when two is always better.

VincentT
04-10-13, 08:48 PM
Well im making 876/860 on a 383 and not running out of turbo yet. I think they are a little on the big side for a stock motor.I think they are going to give up right at 1kwhp

Any reliability issues with that stroker?

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A turbo is like a hooker.... Why have one when two is always better.

Turbos are like hookers? You mean many of them are under age and forced to work under threat of death at the hands of a pimp?

lilgCTS-V
04-10-13, 09:42 PM
im throwing around doing a single 76mm comp oil-less to to maybe keep costs down but i dont want an on off switch meaning i dont want to have alot of lag then a tone of power my cuzins skyline is like that and although cool it wasnt easy driving a right hand drive car in stick, i dont want to boost to fall off then have to respool

VincentT
04-10-13, 10:02 PM
How much engine work are you planning on?

lilgCTS-V
04-10-13, 10:09 PM
well i never had the money to do a build being a broke college student but now that im going to be working full time i might just go balls the the wall, my mentality is yea i could buy a new v2 or something like that or i can do something really really cool,,, to answer your question i want to do 80 lb injectors and a fuel pump and run up 8-10 psi on a stock motor with meth, if it lasts then god bless the stocker but if it lets go i will go iron block.

VincentT
04-10-13, 10:20 PM
I'm mainly asking because the stock block only takes 4 bolt per cylinder heads, which probably would only take about 15 psi without taking risks of lifting. I don't think you really need a 76mm turbo to get 15 psi (any experts, feel free to correct me). It will take a little longer to spool up, and once it has spooled, you quickly have to start draining a lot from the waste gate because you'll be pushing too much air. If you go with slightly smaller, around 70 mm, you should spool a little faster and start hitting 15 psi at an earlier RPM range without having to drain off as much through the waste gate as early on.

I welcome correction from anyone on this because I'm still working it out as well.

lilgCTS-V
04-10-13, 10:23 PM
i think the problem with a 70mm would be that it would "run out of breathe" and i dont know if it would push enough CFM's

robojesus
04-10-13, 10:39 PM
Why isn't anyone here considering a single, smaller turbocharger that could net a yield like a maggie?

This is just my theory, but, it's very difficult to fit a bay mount turbo in the car. Not impossible, but it's difficult. you're running a manifold to the back from one side to feed the engine, so why have one header and one manifold, especially since one would think you're going to need to channel the header into the manifold anyway? just run 2 exhaust manifolds back and twin turbo the bitch... hopefully my theory is correct. not very familiar with turbo.

VincentT
04-10-13, 10:52 PM
This is just my theory, but, it's very difficult to fit a bay mount turbo in the car. Not impossible, but it's difficult. you're running a manifold to the back from one side to feed the engine, so why have one header and one manifold, especially since one would think you're going to need to channel the header into the manifold anyway? just run 2 exhaust manifolds back and twin turbo the bitch... hopefully my theory is correct. not very familiar with turbo.

I have to admit that I'm not really sure what you are talking about.

philistine
04-10-13, 11:47 PM
I think the centrifugal SC's would satisfy the single turbo option. I believe the torque is less pronounced...not sure though since I have no experience with it. The somewhat gentle drivetrain of the V1 would better suit a single turbo...if there was ample room.

runsfromdacops
04-11-13, 02:53 AM
you guys are high if you think your getting a turbo into the engine bay.

i looked at putting my turbos up front the 2nd time around and there really isnt a good way to do it with out alot of cuting/welding on the car.

and the single vs twin thing is just crazy to me, if you want a track only car sure the big single is the way to go. but for a street car it can only be twins.

SCs are fine for low hp apps but are not the best optinon for a high hp street car (ie)hard to control boost in the lower gears with out making a lot of heat for no reason.


idk who said you cant run more then 15 psi on 4 bolt heads but thats just crap im on 18 and doing just fine with oem 4 bolt heads and block (there are tons in 25+ psi range) it has more to do with timing then boost to avoid lifting the heads.

thats all i got for now, im off to bed

-alex

lilgCTS-V
04-11-13, 11:01 AM
you guys are high if you think your getting a turbo into the engine bay.

i looked at putting my turbos up front the 2nd time around and there really isnt a good way to do it with out alot of cuting/welding on the car.

and the single vs twin thing is just crazy to me, if you want a track only car sure the big single is the way to go. but for a street car it can only be twins.

SCs are fine for low hp apps but are not the best optinon for a high hp street car (ie)hard to control boost in the lower gears with out making a lot of heat for no reason.


idk who said you cant run more then 15 psi on 4 bolt heads but thats just crap im on 18 and doing just fine with oem 4 bolt heads and block (there are tons in 25+ psi range) it has more to do with timing then boost to avoid lifting the heads.

thats all i got for now, im off to bed

-alex

thank you! ive also seen plenty of got guys running your amount of boost with the stock heads im not worried about a top end at all i know what these engines are capable of, for christ sake that tt V from colorado ran 13 psi on a completely stock motor and as far as i know its still together !!!

RyRidesMotoX
04-11-13, 12:48 PM
A turbo puts less stress on the motor and less heat in the air charge so you can run more boost. 13 psi is not that much depending on what fuel you are running e85 is great for boost. Also, looking at it from a standpoint of psi(g) is misleading. Compressing air in a state like Colorado that is mostly several thousand feet above sea level is a lot different that compressing air here at sea level in California. Google the BAR measurement. It is a better analog for manifold pressure than psi is as a measuring tool.

rand49er
04-11-13, 06:16 PM
A turbo puts less stress on the motor and less heat in the air charge so you can run more boost. 13 psi is not that much depending on what fuel you are running e85 is great for boost. Also, looking at it from a standpoint of psi(g) is misleading. Compressing air in a state like Colorado that is mostly several thousand feet above sea level is a lot different that compressing air here at sea level in California. Google the BAR measurement. It is a better analog for manifold pressure than psi is as a measuring tool.Not sure I fully agree. If the stress is less with a turbo (as compared to a SC), then it is very marginally less. When you put work into compressing air, it takes the same amount of work to do a given amount of compressing regardless of the method, unless that method is much less efficient and I don't see a turbo and a SC as being that much different as far as efficiency goes. (I did read a thread here where it was stated that some of the newer turbo designs did put less heat in the compressed air delivered to the intakes, but it was not great IIRC.)

Also, isn't it the atmospheric contribution that's less at altitude, not the boost contribution? So, if atmospheric pressure is about 11.5 psi in Denver compared to about 14.7 psi at sea level, 13 psi of boost will be like 24.5 psi total pressure acting at the intake port in Denver vs 27.7 psi at sea level. Am I thinking correctly?

RyRidesMotoX
04-11-13, 09:47 PM
Not sure I fully agree. If the stress is less with a turbo (as compared to a SC), then it is very marginally less. When you put work into compressing air, it takes the same amount of work to do a given amount of compressing regardless of the method, unless that method is much less efficient and I don't see a turbo and a SC as being that much different as far as efficiency goes. (I did read a thread here where it was stated that some of the newer turbo designs did put less heat in the compressed air delivered to the intakes, but it was not great IIRC.)

Also, isn't it the atmospheric contribution that's less at altitude, not the boost contribution? So, if atmospheric pressure is about 11.5 psi in Denver compared to about 14.7 psi at sea level, 13 psi of boost will be like 24.5 psi total pressure acting at the intake port in Denver vs 27.7 psi at sea level. Am I thinking correctly?

My reasoning for saying that a turbo stresses a motor less is because of two things. One, it creates less heat at a given boost level, 2 it has less parasitic drag. My reasoning may be miles off but heat and parasitic drag make the motor work harder. I dunno, that's my reasoning anyways as flawed as it may be.

As far as the atmospheric differences at different altitudes, I would sat that your description is how I should have said it. As far as my understanding goes, that is correct.