Barry Johnson

Hmm, deleted posts? Hehe, all I see are Heinrich's responses and nothing in between them

Anyone answer Chris's posted questions? I can chime in if not...

heinrich

Thanks Barry. No, please man, I was just having a little unwelcome fun.

Barry Johnson

Well allllright!

Turbo sizing and pipe diameter... Depends on the engine you have!
For the 16v guys (US spec) I'd say something equivalent to a GT25/28 would be good, for what I'd run at least (less than 10psi). And, for piping you'd be fine with 2.5" to the hot-side, and I run 2.5" for the cold-side as well on my '79. You should up the exhaust pipe to the hot to 3" since you'll be putting out bigger numbers under boost, but I ran 2.5" for testing purposes.

I'd run 3.5" pipe to the turbo (hotside) for the '85+ motors for sure, since you're already up 60hp compared to the early motors. Run 3" to the intake.
For turbo selection, still judging for a lower boost application, I'd probably go with the GT30 and that would rock pretty hard with the 85-86 cams.

On the S4s and later motors, you might run into some creative turbo fitment issues in the back of the car. Running my little turbo on the '79 provided some funky orientation to make it fit. If you can fit it,
Run 3.5"+ to the hotside, preferably 4" if you can manage. Actually, I'd probably run a dual 2.5" or dual 3" into a big y-pipe to run the end of the exhaust run into a fat single pipe to the hotside. For the intake pipe to the motor from turbo (coldside), you'll definitely run into some fitment issues. If you can fit 4" pipe under the car into the intake, then go for it, I really don't know how (been a while since I was under a later 928). Maybe Y from the turbo to a couple 2.5" pipes that Y back into one fatty (4") at the MAF or somewhere at the front of the car, to make pipe routing and fitment a little more manageable. I'm just thinking it would be easier to route a couple 2.5" pipes than one 4" under the car.
For the actual turbo, personally I'd look into something like whats in my avatar. A T04 .7 A/R with P-trim. GT35 would be awesome, however you can do a GT30 with a larger hotside and be fine. I'd be interested to see how a K27/11 from a mid 90s 911 turbo would do... That has a big hotside, and has enough output for 10psi or lower I would think.

Oh yeah, and for oil pressure, I'd run pretty low pressure myself. Garrett's dont like high pressure, so run a small scavenge pump to recirculate the oil. DO NOT run straight from the motor to the turbo, way too high of pressure, trust me on that .

All of this is from my own opinion of course, and if I'm wrong on any of it, which is possible/probable, voice your experienced opinion and maybe we can all learn something.

Chris Lockhart

Thanks Barry. I'm planning on a separate oil system for the turbo. What do you consider low pressure?? I was thinkinh that a constant 20 psi should work fine, but I wasn't totally sure.

As for the piping size, I thought that you were supposed to run smaller pipe than that to keep the pressure up???? I was thinking 3" to the hot side, and 2.5" from the coldside to the engine with an adaptor to the roughly 4" MAF.

Tom, what sizes are you using on the test mule?????

Lance J

hey chris i'm putting together the same set as barry. on my 79. I'm doing a standalone oiling system for my turbo also. i'm may go with a t04 or a k 27/8. the pressure depends on the specs. of your turbo. like barry said his garret didnt like high pressure. my oil system includes: oil cooler, filter setup, lines, pump, and mics fittings, also i'm wiring up a second pressure meter. i'm gonna relocate my battery and unbolt my battery box to open up space

Barry Johnson

Hey Chris,
The pipe pressurizes almost immediately, however since its low boost especially going for a longer run, I wouldn't go over 3", but then you can expand it at your MAF. Ignore the 4" comment, I have a lot on my mind . Outside of boost, you're still sucking in your normal air for the engine, and these are V8s that like their airflow, so theres probably no 'real' way to know for sure until side-by-sides are done, but we've probably got a pretty good baseline to go off of here
20psi would be fine. I was thinking about running the same actually . Were you looking at the Shurflo pump too?
3.5" would be better to the hotside if you can. Your GT runs something around dual 2.25" exhaust as is IIRC, so a 3" would be a little bit of a constriction, I think. Plus, with the boost you'll be making more hp, so you'd want to open the exhaust up a little more anyway...

Lance J

my 79 has twin 2.25" pipes. so i'm just gonna run it normal all the way to the back and into a 3" y-pipe just b4 were the muffler used to be. into the hotside of the turbo then a single 3" to the front out of the coolside. so my exhaust system will go like this starting from the front rear: 85.5 manifolds W/spacer, x-pipe, (no cats),twin striaght pipes, 3" y-pipe , t04 turbo, 3" outlet to, intercooler, to intake adapter (from carl). i will be running
6psi w/o intercooler, est. power 290rwhp
8 psi w/intercooler, est power 335 rwhp
and 12 psi w/intercooler&propane injection. 400rwhp
numbers may be very optimistic numbers but hey. what ever i lack i'll make up with nos. lol

Chris Lockhart

Sounds like a good plan Lance. I haven't selected an oil pump yet. I planned on running the return line to a cooler, then to a reservoir in the spare tire well, then to the pump, then the oil pressure sender, and back into the turbo. I actually hadn't thought about adding a filter, until you mentioned it. Thanks for the tip.

Barry, I'm currently running MSDS headers into a 3" DR. Gas X-pipe, then I have it necked down into 2.5" pipes, through 2 Spintech mufflers (where the resonators normally reside) then out through a 928 SP RMB. Sounds absolutely awesome as it is. I guess I'll check on a 3.5" mandrell bend universal exhaust kit. I was thinking about thin wall aluminum pipe for the cold side, vs heavy guage exhaust pipe. What do you think???? Also, I saw in a Mustang mag where they are doing the rear mount idea also. They are using the T3/T4 turbo for the 5.0 and 4.6 applications. Would that be a good choice for my application????

Also, what brand of BOV is a good quality component, yet still reasonable in price????

I have all of my drawings/plans for my set-up, and am now in the phase of selecting actuall p/n's of the components, as well as vendor pricing. I plan to piece meal the small stuff, a little each week, and then buy the larger more expensive components with tax refund money. I truly want to get it done and totally dialed in before June. We'll see. Keeping fingers crossed. Thanks again for any/all input.

928BC

Anyone have pictures of a rear mounted turbo?

Lance J

CHRIS i'm in the same stage as you. talk to barry. i got a rough list of what i needed. right now i'm putting the oil system in place. so its ready for the turbo. re-locating the battery to the back seat with a cover. no back seats for me. i'm creating a list, just to track my money for the sake of telling others wheres the best deals on the parts. i'm shooting for 3k as the final cost. the turbo you mention is fine. i'm luck i have 8.5:1 compression ratio. hehe.

Barry Johnson

Hey Chris, other than weight, what are you thinking with the thin pipe? I'm no thermal engineer or anything, but would the thicker walled pipe keep things cooler? Is the thinner pipe easier to work with? Inquiring minds want to know
What are the specs on the T3/T4 you're thinking of?
For a good and reasonably priced BOV, the EVOs are good. http://www.paragon-products.com/product_p/ebdv18-s.htm to get one at a good price

Tom. M

The turbo on my GT is oiled by an adapter plate at the oil filter (thanks Louie). This one is modifed to only provide oil...not return oil. It has one port blocked off and the other one is throttled down at the adapter plate to the size of the line...which I believe is about 1/4 inch braided stainless wrapped. This runs back to the turbo and is returned by a scavenger pump at the turbo into a 1/2 inch id (I think) rubber line that feeds forward to the motor..around the passenger side and into a 90 degree elbow that I tapped into the side of the pan. This was done since access to drill the top of the pan was not there. No issues with the oiling setup in over 4k miles....except for the noise of the scavenger pump which is wired to run when the ignition is on.

Later,
Tom

Now that I have DR's air/oil separator I will likely T the oil return line and feed the oil drain from the air/oil separator into there.... The hope is that the vacuum effect of the return oil in the line will provide suction to clear the air/oil separator accumulated oil...

DR

Chris,

>Also, what brand of BOV is a good quality component, yet still reasonable in price????

The Factory Bosch 944 Turbo/911 Turbo version should be fine, we get them thru OEM suppliers for around $30 or so, I have one or 2 in stock.

OH, BTW the expensive aluminum versions you see are a direct copy of the Bosch unit design.

DR

Hi Tom,

>Now that I have DR's air/oil separator I will likely T the oil return line and feed the oil drain from the air/oil separator into there....
>The hope is that the vacuum effect of the return oil in the line will provide suction to clear the air/oil separator accumulated oil...

Great idea, let us know how that works out!

Imo000

I’ve tried to use 2 similar bypass valves on my car and found them way too small for the SC setup. Even though I had 2 on at the same time, they couldn’t vent enough when the throttle closed. However I think that they might be large enough in a turbo application. For Sc applications a large race type bypass valve (~1.5” dia.) works really well. The HKS Race Bypass valve seem to work for me.

On a side note, Chrysler has the same style bypass valve on all the intercooled turbo engine cars (pre SRT-4). I found one at the local wrecking yard and it was in the air filer box of an early 90’s Daytona Shelby Turbo II. The first generation Ford Probe GT Turbo and Mazda MX6 Turbo has a similar bypass valve too and so do all the Nissan 300ZX TTs.