Ok I just want to make sure I've thought of everything and haven't forgotten anything. I'm planning a single turbo build for my 2002 Z28. I'm looking into picking up a premade LS1 exhaust system for a front mount T4 turbo. I'm also getting a T4, 4psi waste gate, intake pluming, BOV, and oil lines for the turbo.

After installing the exhaust, turbo, and waste gate I plan to "T" off the oil pressure sensor port for an oil feed. For an oil return I wan planning on drilling a hole high up in the oil pan and pluming in a simple return line. After mounting the intercooler in the bumper and installing all the boost tubing with BOV is where the questions begin. Can I mount my MAF in the suction side or does it have to be in the boost side. Also after everything is all hooked up and I take it down to the shop to have it tuned, can I tune the stock ECU or is it necessary to pick up a stand alone system? Will my stock injectors be sufficient with just a tune on the ECU or will I need to pick up something like a set of 60#ers? One last question...For the stock internals is 4psi a good number or can I go any higher. I hope to get some kind of mileage out of the set up...The car only has 42,000 on it as of now.

 

'T-ing' into the oil pressure sending unit doesn't sound like a problem. The Vortech guys run the return back into the pan on the LT1. I wouldn't think this would be an issue on an LS1. You can check out Vortech superchargers online. I know they post the install manual for the LT1 car. They might have the LS1 instructions on there too which could give you some ideas for the drain size, location, sealing, etc. I would recommend a flexible steel braided line for the feed (either -3 or -4) and a flexible drain line. The drain is low pressure so you can use something cheap like heater hose from an auto parts store. Make sure to stay above 0.5" ID and in a nice swooping bend. Bigger is better here. Keep the drain port in the center section of the turbo +/- 30 degrees from vertical.

The MAF should be placed on the pressure side for three reasons.
1) Restrictions in the inlet path (MAF) will have less negative effect on airflow when placed on the high pressure side of the compressor.
2) When running either a Bypass valve or Blow off valve and dumping air to the atmosphere - You want to dump the air before it gets measured by the meter and before the computer makes it's assumptions. If you measure first, then bypass it, then the computer has already accounted for this air - and it never gets to the motor.
3) You can run on the inlet side but if you do then you should not vent to the atmosphere. You should run the bypassed air back to a post-MAF position on the inlet so that what ever the meter calculates is going in - actually goes in. Well this is hot (recently compressed) air. So you end up circulating hot air back into the turbo.
Usually this is more critical on your typically 'Bypassed' ie blower car but still holds true for the BOV. I don’t see any reason to run the MAF on the inlet of any compressor though. Just run the valve before the MAF on the pressure side.

You can run the stock ECU with tuning. You can take your car to a good shop and have it tuned on the dyno.

Stock injectors will not work unless you run an FMU like the device that ATI or Vortech supply with their kits. I’ve found that an FMU will work ok with a turbo because it functions as a manifold-pressure referenced fuel pressure regulator giving you fuel proportional to boost/load. But these are crude devices usually giving you more fuel than you need and should not be run on setups with more than 9psi or so. The 60# Mototron/Siemans are a good bet.

Usually 6-8psi with a good (safe/rich) tune on a stock intercooled motor. 4psi is pretty worthless IMO.

-Scott.

 

I would also suggest an oil restrictor. I had -4 running to my turbo and everytime i got on it, it would blow blue smoke. I took a nitrous jet and opened the -4an male fitting up so the jet would fit in, then drilled the jet with a .062 drill bit. Then threaded the oil line back on (the nos jet has the same taper so it will seal)
Now I have no issues!

Turbos dont need much oil apparently, so I read on the turboforums. Alot of guys run .040-.060 restrictors

Jay

 

Wow thank you guys for such detail. This is exactly what I was looking for. One other question on the MAF. Will a stock MAF be able to understand the air flow readings under boost. I figure air flow is airflow to the meter, but I just want to make sure.

6-8psi on a stock set-up is ok? I was worried about boosting that high on 10.1:1 compression.

I'm looking at some 60# injectors on E-Bay to add to my set-up. Any other info that comes to mind is much appreciated. Once again thank you for the help

-Mike

 

Mike,

Yup. Airflow is airflow. One draw back is that a MAF can only interpret airflow up to certain limit. Once you flow beyond this, you have to manipulate the PE tables in the PCM to compensate. Another option is to run a 2-bar speed density setup (or 3-bar on your LS1). I don't have much experience (if any) with tuning for either - but the SD setup has some real positives in theory. Fuel and timing can be referenced to engine load (boost) and not just rpm like a PE table. With a turbo, you can have 6psi at 3500 rpm or 6psi at 5000 rpm and both conditions require different amounts of fuel. With the PE manipulation you give yourself more fuel per rpm after the MAF maxes - this works great for a supercharged car because the compressor is mechanically linked to the engine and it's rpm. In contrast the turbo is 'load' driven.

Check out that 'other' site for more info. Er, um LS.... dot com.

-Scott.