First, there is a big difference in pipe length. Lets see, if you decide to not run an intercooler on both a front mount and rearmount... its about 4 feet of pipe for the front mounts 15 feet for the rearmount. Thats a difference, but that isnt what necessarily makes it spool slower.

The major reason for slow spool is the exhaust gas temps are lower by the time it reaches the rear of the car. I have been in both front and rearmounts. One particluar vehicle had a T70 rearmount and he swapped to a T88 frontmount ... it spools to full boost sooner.

Put a T70 on a reamount setup and a T70 on the same car with a frontmount and you will see a huge difference in spool time... not even close in fact. They will make similar peak #'s, but peak #'s dont win races.

Nature of physics. Make no mistake, rearmounts can make power and with a good auto setup they can run good at the strip.

 

i was considering a rear mount, solely on the fact i just went out last summer and bought an entire exhaust. if front mounts will get me down the track a lot faster. i will want to go with that. if rear mounts give great power and times ill just go with that. has anyone seen a rear mount ran at a track?

 

Unless they are setup with an auto/stall and two step... they dont USUALLY put out the track numbers one would expect from there dyno numbers. Again, this is due to the peaky powerband.

 

Interesting thread for me. I've been knocking around the idea of a diy rear mount turbo. I'm not so worried about turbo lag while on the street because I don't drive the car much. My main concern is having a decent launch at the track.

 

fortunately i have an auto. what kind of stall would i need to make this functional? i could always 75shot it during lag?

 

Rearmounts can be fun and be fast... make no mistake. When there was a statement that front mount and rearmount performing the same... I had to chime in. They are not equal.

 

Anyone seen a good time with a rear mount at the tracks?

 

The most important thing is a two step (stutter box). Its a built in rev limiter when your not moving. It acts like a rev limiter bogging the engine which loads it and helps spool the turbo while at the line. The will allow you to launch under boost.

 

For track times/performance numbers, just look thru the boosted list in the FI section (LS1's only, but it will show conclusive results). You can see who is doing what with which combo (frontmount, rearmount, s/c).

 

okay, well in that arguement i did say variables... nitrous oxide is a nice way for faster spool. i can argue all night, the fact of the matter is do what you prefer. egt is a small factor in the spool time. if you play your numbers right, match parts to your specific application, spool time can be cut down to a minimum even with a rear mount setup. last vehicle i drove with a rear mount was an lt1 with a large charger, and it peaked boost and spooled around 1800 rpm. i believe that is plenty fast enough. as i stated before... MANY VARIABLES. if we want to get technical, use nitrous for a faster spool, locate the charger closer to the catalytic converter, get a different trim, different diameter piping... and the statement about the intercooler, i believe on a custom fab kit it is pretty damn rare to NOT use an intercooler in a front mount setup due to higher temps around the bay, as far as rear mount the piping almost plays as a cooler under the vehicle. back on topic, sorry to bash but i dont like being called out. hopefully this will help your decision

 

to add to the topic though, imo for myself... rear mount is easier to fab and more cost efficient for my pocket and with the resources i have around me. if you want to do a front mount setup, more power to you. please do not mistake and take it as i am saying one is better than the other, but i have seen both sides of the table and played with both. i HAVE seen equal performance between the two

 

Exhaust gas temp is the major factor in getting that turbine wheel to spin.

I agree 100%

Umm... no it didnt peak boost at 1800rpm. Perhaps you didnt mean to say that... unless the turbo was ridiculously small for a 350ci engine.

First... front mount wouldnt need the nitrous to spool. Second, moving the turbo closer to the cat would help with exhaust gas... but now you have 1" of ground clearance moving it closer to the cat. You could get smaller A/r turbine housing and smaller diameter tubing... but now you bare choking the top end ... which wont let you make the same power as the fontmount with the same turbo, bigger A/r turbine housing, and nice big charge piping.

I tried to make it easy for you to understand, but it went over your head. Lets assume both cars have an intercooler, as its silly for a STS setup not to have an intercooler too. Lets assume the front mount turbo is located where the smog pump (same place the charge piping for the STS kit comes too from the rear). The piping would come out of the turbo, into the intercooler, out of the intercooler and into the TB. Now, the intercooled StS kit would take the same route, but start from the back of the car... atleast double the distance away.

The piping doesnt provide that much cooling... sales gimmick by STS. If the pipes are powdercoated or ceramic coated, they retain the temp inside the pipe... thus throwing the cooling affect out the window.

LoL... you need to do some reading bro. Lots of what you say is wrong. We were all like that early on, the more experience you get, the more info you read, the clearer it will be.

Do a search in the FI section here or on cz28.com and you will read alot about STS setups. I am defended STS for a long time, but the truth is just that... Front mount > rearmount.

 

Thats the right way to go about saying it.

You have stated they are equal before.

There it is... your saying they are equal again

 

okay... you win the arguement. after i read what i posted, my text doesnt make a bunch of sense. btw i am not a noob, i work on stock vehicles... but if you feel that way, doesnt affect me

 

i have my ideas, and i guess trial and error will justify it in my head. so what if i blow a ****-ton of money, thats why we tinker right??

 

I've had both the front mount and rear mount, here is my opinion...

Rear mount:

forged 355, 8.8:1 compression
le3 heads
futral custom cam
yank 3600 stall
built 4l60e
3.73's
255/50/16 mt dr's

All custom build rear mount by myself and a buddy
MP T70 .84 ar
2.5" stainless charge pipe
3 1/2" downpipe
stock exhaust manifolds/ypipe/I pipe
FMIC
tial 50mm bov
tial 44 mm wastegate.

Front mount: (current setup)
Stock lt1 with just forged rods/pistons 9.5:1 compression
th400/4000 nitrous stall(very tight)
3.42's
255/50/16 mt dr's

RealQuick's log manifold setup
Turbonetics T76 ball bearing .81 ar
3" charge pipe
FMIC
Tial 44mm wastegate
RFL BOV

The rear mount setup was on 7psi and had a lot MORE lag time than my front mount on 8psi(I turned it back down to 6psi for now since I was maxing out my injectors).

The rear setup had A LOT better heads/cam, stall ended up being about the same, rear had a smaller turbo, but still didn't spool as fast.

I actually have LESS money in my front mount setup that I did in the rear mount setup, and A LOT less time. The front mount setup went on easily, I got the hot parts from RealQuick and had the car running in one day, ohh...and I did go to work so I didn't get to work on it for 8hrs of the day. I got the kit at 4pm on a Thursday, and had it out on the streets driving on Friday night.

That being said, I do think rear mounts work(thus why I built one before), but just not nearly as good as a front mount, and definitely isn't any cheaper.

 

If i go with rear mount, i shouldnt have a huge lag with proper Stall, and 2-step?
I was planning on using the nitrous off the line.

 

You can spray it to get rid of the lag, but at that point, why not sell the nitrous kit and just use that money to get a front mount setup.

My rear mount setup had $3200 in it with me doing ALL THE WORK.
My front mount setup has about $2800 in it, with Real Quick building the headers/crossover.

 

No trying to pick on you dude. I wasnt calling you a noob either, you just need to do some more reading/learning. We have all been there.

 

whatever happens i will let you guys know the results! thanks for the advice!