1994 Infiniti Q45 Rear Mount Turbo full writeup w/pics

[qsiguy]

There's a teaser thread about this but it's on the road now so I thought I'd do a more complete write up with details of the project. I'm using a T70 Master Power turbo, Tial wastegate, and tial BOV. I'm using a Shurflo 8000 series pump to scavenge the oil from the turbo. I have done all the fabrication and installation myself and think it turned out nice.

The car sounds awesome and pulls hard with only a 3.6PSI wastegate spring. My goal is to get it tuned up to 8 PSI on the stage 2 boost controller. I'm at full boost around 3k or less and it spools pretty quickly. If I'm rolling at about 15-20 mph already it'll hit full boost in about 2 seconds or less if I'm going faster to start with.

Here are some photos of the install process. As they say a pictures worth a thousand words....

This is the muffler that was replaced by the turbo.

Here's my T4 Flange pipe

The is the Y pipe I made to join the OEM dual exhaust

Here's an early test fit of the turbo

Y pipe installation

Here's the exhaust extension w/T4 Flange and flex joints

Extension pipe installation

Here's the compressor tubing

Final mounting and oil lines

Oil feed from filter sandwich plate

Oil pressure sending unit and feed flow needle valve

Oil return line w/modified fuel filter as oil return sightglass

Final mounting

Final mounting with chrome tips

Exhaust heat wrapped and painted compressor tubing.

Gauges

Here's a few videos, I'll do some more and post, I'm not happy with how these came out. Can't hear the turbo good enough and that's the coolest part!Revving in park

High speed flyby

BOV demo.

The oil pump is in the trunk and still needs to be permanently mounted as of the time of this post. I'll post a pic of it when it's done. Still have a few small items to complete and get to work on the tuning so I can turn up the boost.

I have tons of pictures so let me know if you want a picture of something specific.
Modified by qsiguy at 10:56 PM 4/4/2009

[Rex]

Great looking write up, be interested to hear about the overall drive-ability.

... I have tons of pictures so let me know if you want a picture of something specific.

a dyno sheet?

[Q45man1]

Congratulations! I tell you job well done. It looks and sounds awesome!I'll be interested how things will hold up and with your know how I think it would be great.

[qsiguy]

Dyno will have to wait, Wes and I are working on the tune for the ECU and I want to get the dual stage boost controller in and working before I do the dyno so I can get both #'s.

Driven it for 3 days now and so far it's awesome and working flawlessly. The only problem encountered so far was on the first test drive. I was short one clamp and left it off the compressor tube where the 2.5" tube joins the 3.5" tube in the front. The first time I made boost and let off throttle the tube popped off. Since it was at night, I pulled into the local WalMart and found a 3.5-4.5" hose clamp, installed it and everything has been working perfectly since.

[pagong]

That is one good looking project. Now its time to enjoy it!

[qsiguy]

Here's a few more pics to add.

Here's a side view of the rear of the car. As you can see the turbo tucks up nicely under the vehicle, stealthy!

Here's what I did with the wastegate. It vents into the right side tip.

And last, here is a shot of the system with the air filter installed. It's a little dirty as I'm using the one I already had on the car for now.

And last, here's the business end of the turbo Q (and what anyone who races me will see!)

[rubdog]

awwwsome!!!!!!!!!!

[irsa76]

Interesting. I'm not completely sold on rear mount turbos, any reason why you went this route? What's the benifit?

[qsiguy]

I have been a believer for a while now and now that I have my own rear mount I'm 100% sold on the rear mount route.

Benefits...1) Ease of installation. You might think it's a pain to run the compressor tubing all the way back up but it wasn't that difficult. Compared to the only other Turbo Q I know of (Siju's) which is a front mount, my install was super easy. He had to move a bunch of components, route exhaust tubing in a loop and come back to the front turbo, then run the exhaust back down and out the rear, and redo pretty much all of the intake system. Haven't measured but he figures he's got close to the same amount of exhaust tubing in front of the turbo as I do.

2) Keeps the engine bay and turbo much cooler, therefore making the turbo last much longer IMO.

3) Intake air temps will be cooler due to the cooler turbo and length of compressor tubing. No need for an intercooler, at least at low boost.

4) Sounds amazing, sounds like I installed a jet engine when I leave the stop light!

5) Cost is about the same or less than a conventional front mount. I still have to add up all the receipts but I am pretty sure I'm around $2.5k-$3k for the project and I got things that aren't required.

People assume you will have terrible turbo lag but that's not correct. If you size the turbo properly it will work exactly the same as a front mount. I obviously don't have boost off the line (as with most turbo vehicles) so it feels exactly the same as it did before the turbo from a dead start but the turbo kicks in quickly and I'm at full boost around 3k or less. At cruising speed I can hit full boost under 2.4k when I tried it this morning. It actually goes into boost at a lower RPM when I accelerate slower. When I go WOT the RPM's come up quick and the turbo takes a second to catchup. When I accelerate at about 1/2 to 3/4 throttle it really pulls and goes into boost around 2.4k. Basically, it all comes down the proper sizing and installation.

I spent a long time installing mine but I've talked to people that have done it in a day or two. They are not as pretty as mine but work well. If you take on a project like this it's up to you how you install it. If you just want it to work you (and maybe a friend or two) could spend a full weekend, once you had all the parts, and have yourself a turbo Q. You need to have some skills and decent tools of course, did lots of welding. In reality, if I add up the total time I spent on the install I probably only spend about a weeks time. It was just spread out over several months since I couldn't work on it as much as I'd have liked to.

[elwesso]

Shane

I want to get your feedback on this possible idea. in light of this rear mount turbo situation, what would you think about cutting out the precats, mounting 2 smaller turbos there and then routing the piping up that way?

I would suspect that you would have to use the scavenge pump and all that stuff, which isnt really a big deal... might be easier that way than have to deal with modifying the sump and all that crap.

The only tricky part would be the plumbing?

[qsiguy]

Boy I don't know. It's pretty tight up there. I have never measured it but even a small turbo I'd think would be hard to fit in there. The crossover compressor tube would be pretty low as well where it goes under the transmission. The only part of the compressor pipe that's been a pain for me was where it goes under the motor and you'd still have to do that same section unless you go up near the steering shaft. Siju did that but he said it was a huge pain and he wouldn't recommend it unless that was the only option.

The long compressor pipe wasn't hard at all and judging from the tight spaces to work with I think putting dual turbos where the pre cats are would be a pain. I guess you'd have to get the measurements for the turbos you wanted to use and start measuring and test fitting stuff. I'm pretty sure my T70 wouldn't fit in there and I'm not sure how much smaller a T4 60 or whatever would be.

Swapping the resonators for turbos might be doable but I don't think that would be any easier than my setup either and you may still have more clearance issues.

This pic doesn't show much but I already had it from when I was plotting out my setup.

[CrimsonQ]

<-----Poor & Jealous.....

very nice, sounds great!! You make many envy..

[sijoko]

Boy I don't know. It's pretty tight up there. I have never measured it but even a small turbo I'd think would be hard to fit in there. The crossover compressor tube would be pretty low as well where it goes under the transmission. The only part of the compressor pipe that's been a pain for me was where it goes under the motor and you'd still have to do that same section unless you go up near the steering shaft. Siju did that but he said it was a huge pain and he wouldn't recommend it unless that was the only option.

The long compressor pipe wasn't hard at all and judging from the tight spaces to work with I think putting dual turbos where the pre cats are would be a pain. I guess you'd have to get the measurements for the turbos you wanted to use and start measuring and test fitting stuff. I'm pretty sure my T70 wouldn't fit in there and I'm not sure how much smaller a T4 60 or whatever would be.

Swapping the resonators for turbos might be doable but I don't think that would be any easier than my setup either and you may still have more clearance issues.

This pic doesn't show much but I already had it from when I was plotting out my setup.

Let me say this as someone who built his own front mount turbo for his Q45: The rear mount is the best setup for most people. It is way easier to fabricate and it is cheaper. The performance potential is more than enough.

Who would ever call a 420 hp Q45 slow? Okay, it is not what most think of when you say the words "turbo system" but it works. In fact, I have plans to build a rear mount for my silver Q.

Props to Shane for building the first rear mount turbo system for the Q45. Now, who's next?

Wes, about your question regarding twins under the car. There is space further back where the main mufflers reside. You just have to use small bodied turbos. Two T3 turbos should get the job done. Clearance will probably be an issue but it would be bearable.

[Jesda]

I posted this on a few other forums. This is freaking SWEET.

[qsiguy]

One more video for you. You can hear the spoolup pretty good in this one.

[qsiguy]

Starting to gather some technical data. Here is a screenshot of ECU Talk under WOT at full boost (3.6psi). Looks like the injectors have a lot of room left as the duty cycle is only 41/39% and the a/f appears rich. Anyone have any comments or thoughts from what you see here? How about you Tech?

I also have the narrow band a/f gauge on the pillar and it shows rich under WOT as well. Anxious to see the actual a/f # from the wideband. I did the 0-60 test on NDS and it was slower by about .5 sec than before the turbo. Hard to compare times tho. The previous time was in about February at night when it was cool w/my stage 1 NICO ECU, today it was 100*F ambient and I had been driving it around for a bit and have the stock ECU running. I'll have to do the 0-60 in a couple months when it cools back off here.

[burijon]

How will you deal with water and that low air filter? Does it matter with a turbo?

[qsiguy]

I have a cover for the air filter that sheds water off the filter. Unless I submerge it I will be fine. Water won't do anything to the turbo itself. Still debating fabbing up a shield between the filter and the tire.

[Scooby24]

Are you monitoring your AFR's? Your MAF is now metering compressed air and is not accurate.

[AlabamaDan]

Amazing project Q. I think my favorite gauge there is MPG = 1.

[qsiguy]

Yes, I had to laugh when I saw that as well.

[elwesso]

Are you monitoring your AFR's? Your MAF is now metering compressed air and is not accurate.

Thats sort of misleading. Technically its measuring the air thats going into the motor, it shouldnt really matter if its compressed or not. if you tune the ECU to run with a blow through MAF you should have no problems, but the fact is the Q45 MAF/ECU was never made to run with boost anyway. Its not about the sensor, its about the way the sensor data is interprited.

So shane, when are you going to throw one of those boost maps on the EEPROM and run 8lbs?

[emoq45]

great stuff man. loving the sound !

[T45]

Awesome job! I have always liked the rear mount concept and think it's better than front mount for non-racing apps. Can't wait to see what kind of power it makes above 5 psi.

As for the shield, I see you live in PHX so rain virtually isn't an issue. I was there for 3 months last summer and it rained one time for about 5 min. LoL

I would however make some kind of alum shield for the assy. to keep debris from striking it. One rock to the oil fitting and if you're not paying attention it's toast.

And since you don't mind cutting the body up at all, I would even go as far as routing the air intake through the rear fender/bumper or up through the trunk and possibly making a scoop in the deck lid. That way you aren't getting the warm/dirty air coming under the car from the radiator and exhaust. I'm sure it won't make a difference in performance but your air filter will thank you for it.

Did you entertain the idea of a separate oil system for the turbo while building it?

[qsiguy]

........Did you entertain the idea of a separate oil system for the turbo while building it?

Yes, and bagged it. I think it would have been much more of a pain to do an independent oiling system. Oil tank, cooler, dual pumps, etc. The only hard part to my system was running the long hoses and that wasn't that bad, only took a few hours. Pump is easy, oil filter sandwich plate easy, return line easy. It was much more difficult in my head thinking about doing it that it really was.

I already made the 2nd stage controller, I just need to hook it to the wastegate reference line and wire it to a switch up front. Then I can slowly turn up the boost. Still sorting out the boost maps and how I want to do it. Also still need to get the wideband installed so I can keep better track of the AFR. I don' t have too much confidence in the OEM O2's and the narrow band gauge even tho it's saying rich under boost.

[T45]

Do you have an oil pressure gauge on the turbo lines in the rear? If a line gets cut or ripped off by some punk you may not be able to tell due to the fact that the engine pressure gauge is basically on it's own circuit.

[qsiguy]

I didn't put a pressure gauge on the rear because there really isn't much pressure on either of the oil lines after the valve in the front. It limits flow/pressure the turbo sees. Also, with the pump drawing out the oil it may very well be under a vacuum. My pump will pull a lot more oil than I am allowing to feed into the turbo. If turbos get too much oil you can blow the seals or at least leak into the turbo making a mess of things. I've heard that's a major cause of turbo failures, too much oil pressure. The return line won't likely have much pressure on it either as it just dumps straight into the valve cover without any restriction. I may check the pressures at some point but I'm not concerned at the moment.

All I can do is keep an eye on the lines and give the car a quick "pre-flight" before I drive it. Watch for oil on the ground etc. If someone wants to vandalize the car they can do any of a dozen things to sabotage the car. I'm not going to worry about it. If it happens it happens. The lines are tucked up very nicely and are pretty thick. I'm not worried too much about something hitting them and causing that much damage. If I ever hit something that hard I'll know it and will check it out before I go any farther.

[CINNALOCKS]

This is off subject but I saw a portion of your steering wheel and I am curious what the leather wrap looks like and where it was done. Would you send me a pic of the steering wheel? [email protected] Thanks

[qsiguy]

hehe, it's actually just a leather slip on from Walmart. I love it, feels good, what inexpensive, and fits good. I liked it so much I got one for my wifes van. In the photos it doesn't look like it matches but in the multi tone interior of the Q it matches nicely.




Modified by qsiguy at 8:21 PM 10/1/2007

[maxnix]

With the amount of heat transferred to the cabin form the muffler, I can't help but wonder if the turbo would cook the spareribs on the way home.

Interesting, but compressible air column keeps coming to mind.

I might have to make a detour to see Sijoko's front set up.