itsslow98

iTrader: (18)

Every turbo setup has connection and boost leak problems at some point no matter what everyone says, if you use good connectors and vband clamps it doesnt matter how many pipes you have.

With the ball bearing and billet wheel turbos available today you can make an 88mm spool just as fast as an old school 60.

Dont get me wrong i would do them like gulfm3 as well but the fact of the matter is the right rear mount setup will be just as efficient.

racebyu

I have not driven a turbo car in many year and back then a Eagle Talon had a huge turbo
lag, guess the new ones have some engineering changes over the last 10+ years.

DrSpeed

iTrader: (4)

You're telling me that with the SAME sized turbo (compressor and exhaust housing), you can build a "KIT" that would have identical...hell, even "comperable" performance with a turbo that is less that 2 feet from the head versus one that sits by the tailpipe?

itsslow98

iTrader: (18)

Yes, I am. They both have there advantages and disadvantages like underhood heat from a front mount turbo compared to a rear mount.

Im not an expert but there are many rear mount setups that you couldnt tell were rear mount if you didnt look and just drove the car.

Main thing i dislike about rear mounts is having to run oil pumps to the turbos, they just add one more component to a system that could fail and be a hassle.

GulfM3

iTrader: (14)

I had a dam novel typed out about rear mount vs conventional front mount and Tech decided to log me out and I lost it I'll try and retype the cliff notes version.

The reason rear mounts suck is because you lose a LOT of thermal energy from the 10' of exhaust pipe running between the manifold and the turbo. You can make up for this by using manifolds over headers, manifolds hold more heat inside the pipe, wrapping the exhaust between the manifold and turbo with fiberglass wrap, and choosing a turbo with a smaller turbine a/r. Smaller a/r turbines will spool quicker in the rpm range at the expense of being more restrictive.

In my build I used the stock manifolds, with a piece of ~1' long schedule 10 stainless steel pipe to connect the manifold to the turbo. Schedule 10 is almost 1/8" thick, and pretty heavy stuff. But I believe the weight penalty is worth it because the thicker metal is going to hold in more heat. Speaking of schedule 10 pipe, take a look at what most reputable custom turbo kit manufactures use to build their custom turbo headers. Even with the schedule 10 pipe my future mod list includes wrapping the connection pipe with fiberglass exhaust wrap. Why? When we were dyno tuning the car we made two pulls, basically back to back (no change was made in the tune itself). The first pull was with a "cool" motor, the car had been sitting for 20-30 minutes with the fans on it. The second pull was after the first pull, we never shut the car off, held the motor at 3k rpm's for a minute revved it a couple times then made the pull with a hot motor. Guess what... the second pull on the hot motor made 20 more hp and spooled the turbo to full boost ~300rpms sooner. Velocity and HEAT is what you need to get your turbo boosting.

Heat soak is an issue on turbo cars, but on any forced induction motor the heat soak you worry about is heat soaking your intercooler, which better be OUTSIDE of your engine bay. Unless your a WRX.... their intercooler setup still blows my mind. You get heat soak issues when you keep the car in boost for too long, even the largest intercoolers will eventually heat soak if you keep the car in boost long enough. Regardless, I don't care what my under-hood temps are so long as I'm not melting wires because my intercooler is getting fresh cool air from the front of the car. Yes I know part of my charge pipe is inside the engine bay, but the amount of time the air spends in the charge pipe inside the hot engine bay is a fraction of a second and insignificant. I would try to route the charge pipe away from the turbos in a front mount turbo setup.

I have never built a rear mount setup, never will. However, I do believe if you built a kit using manifolds, wrapped exhaust pipe and the correct sized turbo you could have a halfway decent street car. There are people who love their rear mount setups. But it's definitely not the best way to build a turbo kit and you are for sure leaving HP on the table. If you are doing a max effort build, such as a texas mile car, you better keep the turbo as close to the exhaust port as possible.


Take the same "properly" sized turbo hanging 6" from the exhaust ports and put it in a rear mount configuration and it will be noticeably slower to spool and it will have a lower maximum boost potential.

Guess I typed another novel.

racebyu

Makes sense if you have a turbo close to your exhaust port then the time for
it to spool up in speed would be much faster then one that is 10' away at the
back of the car. To increase boost you have to increase the pressure in the
exhaust tube which will make the turbo spin faster, its much easier and faster
to increase a 2.5" dia tube that is 12" long then one that is 10' long as its based
volume of the two tubes. The rear mounted turbo would have to be slower at
spooling vs the one located directly at the exhaust port, would it be much? who
knows could be in the tenths or hundreds of a second difference. Smaller turbos
have a smaller impeller and mass so the spool-up time would be reduced along
with a smaller dia piping could help reduce this lag.
Either way the car has a huge potential of creating tons of power and would be
a blast to drive

willsol

Well I was thinking a little lag would be good for these cars and take a little stress off the diff. I was thinking about just a single turbo though sized correctly. All I would like is 500 crank hp.

racebyu

Dont think it will take any stress off the diff just that there will be a delay in
when the engine kicks in after you mash the pedal, could be very minimal or
actually noticable, dont know?

TheLS1Lover

Truck manifold kit /thread.

rand49er

Agree wholeheartedly.

All this quicker spooling turbo talk does not make up for the distance issue. You can take those same so-called quicker spooling turbos and mount them close to the exhaust ports and they'll perform better, plain and simple ... lag-wise and efficiency-wise.

Don't get me wrong, I'm sure rear-mounted turbos are probably a blast to drive compared to stock, but they're not optimal.

4doortypels

iTrader: (39)

agreed, its not as efficient, but that doesnt mean they dont make power, a little lag may provide a little traction... im planing on a single turbo 402 or 408, on my next V... getting the parts together while i dont have a payment, my buddies and me are gonna try something under the hood, even tho i havent seen any successful attempts... but we will get to that bridge when it gets there

CTSVBiggie

iTrader: (1)

having mine for a week.. And I cant understand the need for turbos on this car yet... Maybe later

JJSimon904

iTrader: (8)

^ The bug will bite you soon...it always does.

itsslow98

iTrader: (18)

Lol, you couldnt be more right. Do your research first though itll save you money and headaches in the end. Thing to remember is you arent modding a 3100lb vette or 3400lb fbody so you have to plan your mods accordingly.

tony tone

****.... after selling my 426whp gsr i wanted to boost mine almost immediately, lol.

one day

DrSpeed

iTrader: (4)

There are too many experts here...no point in adding my 2 cents.

...you know the ones...you explain heat transfer, energy content, pumping losses, changes in turbine housings...but they still say it doesn't make a difference.

liqidvenom

iTrader: (2)

when building a turbo kit for a vehicle the argument that is one turbo in x location makes more power then if it was mounted else where. You can build a kit that would reduce lag time and have the setup make power. in most cars you have to make a sacrifice when it comes to fresh air inlet, turbo location, turbo sizing, exhaust routing, charge air routing, "intercooler" setup, etc. if someone is happy, and many are with their rear mount, then thats what really matters.

Our chassis doesnt really allow for setups which are popular on other chassis. heck look at the number of people who act like those tiny maggie blowers are such a great way to make power. but if the owners are happy then why is it a bad thing.

I have driven a few proper setup rear mount turbo vehicles on 4cy, 6cy and 8cy motors. I would have no problem running one on my car.

ColeGraham

iTrader: (8)

that tiny Maggie is the best way to get quick (big) power to our cars. they are most cost and time effective then doing another F/I setup. most of us (myself included now) DD the car, and cant afford to have it tied up in the shop (or our garages) for several weeks getting a TT, single turbo, Procharger set up. i know that if i cant drive my car for 3 weeks, i would be pissed have to walk 12 miles to work, and 12 miles back.

rand49er

Is there another FI kit that a guy having as the most sophisticated tool being a torque wrench can slap on in a few days of tinkering around next to his lawnmower and the kids' bikes and get well over 100 rwhp gain with ZERO lag and not have to deal with custom fabricating nearly 30 feet or more of plumbing and that is completely reversible and has no degradation in driveability?

ColeGraham

iTrader: (8)

NOS (sorta)...haha...but that bottle emptys pretty quick when you hit the go fast button.

but there in all seriousness, no there isnt. thats why i like the Maggie option. but i am going a different route now with my car. not going to go F/I, going to stay N/A with H/C/I and be done. or just buy a C6Z...