Tuning with turbo (SD22 / '85 kc 4x4)

#1

Ok, test drove my turbo swap today and got some first try results. The linkage on the turbo was backed all the way off and all fuel settings were stock. I dont know a water temp, my guage broke but it will be fixed ASAP.

(SD22 from an 82kc swapped into an 85kc 4x4.)

I am pulling about 4-5 PSI
EGT is running 850-900 when climbing a hill

I wanted to pull more boost but those temps scare me a little, I kept backing off of it to keep it down a little.

What are the suggestions? I think if I adjust for more boost the temps are only going to go up right?

#2

bacho wrote:What are the suggestions? I think if I adjust for more boost the temps are only going to go up right?

I think adding more air will cool the EGT, since you're not adding more fuel. This is counteracted a bit by the compression of intake air raising its temp, but I would think overall that the EGT would come down.

Do try it and tell us!

Is your thermocouple before or after the turbo? Either way, that's a good range to run in.

#3

IIRC many folks running turbos on IDI motors routinely see numbers at least that high on climbs. It seems like alot of folks looking for big power are willing to flirt with pre turbine temps of 1050. Not that I'm advocating this, but I think that 900 sounds fine.

Do you have good idea what the fuel economy numbers were before the turbo? I'm very curious to see how it's affected. How's the power?

Sounds fun.

#4

I will go out and run it up some more, I am kinda scared though because I dont have a water temp working so I have no idea what thats doing.

I have read that 1250-1300 is a safe cruise (via banks) is there any major difference between a cummins or a powerstroke and an sd22 for those temps?

#5

I have often heard 1100 or 1150 quoted as the MAX you should be willing to accept, but that's just my memory. I might go a little easier on the little SD than a 6bt. Just my $.02

Got any photos?

#6

Ran it one more time before it got too dark (no tail lights) I adustet the waste gate and was running 7psi. It had much more grunt there and the temp seemed to be a tad better, but I didnt run it long enough to tell. The waste gate linkage came off one side because it was missing a c-clip. So I got to experiance what 7psi was like and what NA was like, The turbo seems to have doubled HP.

I am not going to run it any more until I get a proper air filter and water temp.

#7

http://www.bankspower.com/Tech_whyegt.cfm

Thats where I saw that. But I will take it a little easier on this old motor, just that 1000 degrees comes really quick on accel.

I dont want to put up any pics till I am done, I got to get a better intake set-up.

#8

bacho wrote:http://www.bankspower.com/Tech_whyegt.cfm

Thats where I saw that.

That's a very good article.

Banks has a lot of experience in this area. They are careful to point out that those figures (1250-1300°F maximum sustained) are measured at the exhaust manifold, between the engine and the turbo. I didn't know that the temp drop through the turbo could be as much as 300°F under heavy load, so I've learned something today.

I want to point out that Banks is talking about OEM turbo setups there (and possibly their add-on turbo kits, it's not clear). OEM turbo engines sometimes have the compression matched for safe turbo operation, and in many cases additional piston crown cooling via oil jets to apply a stream of oil to the underside of the pistons. Those two factors alone would give a heavy safety margin for running at a higher EGT. Intercooling (cooling the intake air that has been heated by the turbo, primarily via compression, and prior to reaching the intake ports) can reduce thermal stress even further. And water injection on an on-demand basis does the same thing: cools intake air.

For a conversion (turbo add-on), more conservative EGT numbers would be prudent.

I dont want to put up any pics till I am done, I got to get a better intake set-up.

Before and after pics are good. I take pics all along the way these days. I don't post them all, but it's helpful to be able to pick and choose from too many photos later. I tend to do several revisions of my own fabrications.

#9

I have some pics, but I dont tend to post pics up in progress because I have found that people get the idea that my temporary stuff is great.

I have been thinking about water injection because I dont have a intercooler but I do have the old water injection stuff from my fathers builds back in the day. I might do it one day, shouldn't be too hard.

#10

I bought a bunch of water injection parts from several sources last year, the stuff has gotten a lot cheaper lately. The one thing I couldn't find to fit my installation was the tank. The pump, solenoids, dual pressure switches (two-stage injection: higher boost = open a second solenoid to a 2nd nozzle), and nozzles were easy to get.

I'm excited that you have actually got yours to the drive-it stage.

#11

asavage wrote: I'm excited that you have actually got yours to the drive-it stage.

Me too!

#12

I'm the most excited.

Mine's a 4x4 so that may have a little to do with this, the motor has to work a little harder pulling 31" tires and 4.10 gears. I plan on swapping in Toyota axles with 5.29 gears after a bit.

#13

asavage wrote:I want to point out that Banks is talking about OEM turbo setups there (and possibly their add-on turbo kits, it's not clear). OEM turbo engines sometimes have the compression matched for safe turbo operation, and in many cases additional piston crown cooling via oil jets to apply a stream of oil to the underside of the pistons. Those two factors alone would give a heavy safety margin for running at a higher EGT. Intercooling (cooling the intake air that has been heated by the turbo, primarily via compression, and prior to reaching the intake ports) can reduce thermal stress even further. And water injection on an on-demand basis does the same thing: cools intake air.

I'll ditto the point Al made about Banks, they've been around for a long time and are highly respected.

I have an SAE paper from VW that mentions some of the revisions they made to the 1.6 D engine to make it a TD. The ones they mention are as follows:

Intake and exhaust valves were modified for higher thermal stress. Modification to valve seat material and materials for the exhaust manifold. Cylinder head and turbo charger mounting bolts materials.

A number of changes were made to the crankshaft. The front end of the crank was reinforced. The highly loaded crank-pin, at cylinder 4, has it's radius induction hardened and the oil hole ground while radii at the other pins are roll hardened. A torsional vibration damper is used.

Oil cooled pistons. Because of higher stress in the piston pin region relief pockets had been cut out.

These are only the ones mentioned in the article, there may be others that weren't talked about. VW uses a blow-off valve on their TD engines too. I have to say I knew that the exhaust valves were different but I wasn't aware that the intake valves were.

Glad to hear your project is moving along well!

steve a

#14

Holy black smoke! This is where all the action is! I've been missing the party!

The Banks article is on the money, but does not address one thing (unless I missed it) that we are concerned with - high compression.

First let me say that while my fab experience is limited to my SD setup, I have done a lot of turbo swapping on my Cummins, spend hours every day for years watching boost/pyro/fuel pressure, and have spent many thousands in repair bills, so I know some of what doesn't work.

There are two separate things going on here. One is damage as a result of high EGT.
I bought a rebuilt big motor once and noticed that I could run the pyro over 1500 easily, so I really had to watch it (rather than just turn the pump down). Even so, every now and then I'd forget, look down and see it up there. I put a mirror on angled so I could watch the top of my stack just to help me (black=hot). After a while I thought I could do better so I put on a different turbo and voila! perfect. I later discovered I had an OEM turbo that was an engineering error, later corrected by Cummins by the retrofitting of a different turbo. But here is a pic of the beginnings of damage compared to new-

The turbine housing and the exhaust manifold will shrink, warp, and crack til exhaust starts going out the cracks (exhaust leak) which causes the turbo to deliver less air, which makes the fuel too rich, which makes the EGT even hotter, and you can see a quickly spiraling disaster. My turbo rebuilder has a pile of such junk. I also want everyone to realize that you can get this kind of damage on a NA motor as well if you turn the pump up and it is blowing black smoke. Put a pyro on and see.

The second and separate problem is that of piston stress. When you start putting more fuel into the cylinder than the factory setting (assume that it is efficiently burned, but the turbo is irrelevant), the rate of cylinder pressure increase during combustion changes. A spike of unacceptably high pressure starts to happen at the beginning of the power stroke (@full throttle). The picture shows the result on a Cummins piston (855cid) which is beside the SD22 piston. A crack begins at the pin bore and works its way up. When it reaches the rings a hole blows through.

This is counteracted by retarding the timing and/or reducing the compression ratio, neither of which we are doing with our motors. Please note that the Cummins blew without any warning, and the pyro never, ever, went anywhere near the limit. Everything was OEM, just with the pump turned up. But to keep from scaring the pants off you, it went a couple hundred thousand miles that way before blowing. That motor was 17/1 cr and ran about 25 lbs boost. It also would run WOT for 5-10 minutes several times every day and maybe 20 minutes once or twice a week.

My personal guess is that ours will do fine with the stock compression and timing at very high boost around town, between gears, getting up the on ramp. I will not be pulling any long hills at over 7 lbs boost, because that's what boost it makes at the factory IP setting. The SD is a tough motor. It already has oil jets that cool the pistons and the bottom end is much beefier than anything VW made. And don't worry too much, I turboed mine in about '95. This is not completely unexplored territory.

If you have a wastegate setting, set it for max. I have mine welded shut. You want all the air it will make. Too much air is not what will hurt, it's too much fuel, with or without enough air to burn it. The only reason for a wastegate on a diesel is if you're going to run a (too) small turbo that gives quick boost on the bottom but opens up on the top to keep from choking the motor. That setup also gives very clean exhaust away from a light and between shifts.

#15

Set the waste gate to max and took it around the block, pulling 8-9psi and its running well, I did not pressurize the IP on mine, that hose is open right now. With the additional boost keeping the pyro in check is easier, its staying about 900 when your on the throttle and will climb higher but not so quickly.

Now I have an issue that I have to shift pretty fast on hard accel to keep the motor from over reving, the boost shoots to about 15 when the gas is let off for a shift, would a BOV help that?I would prefer to kill that over rev.

I will get better pics and a video soon, I really want the water temp gauge and a better air filter before I run it much more.

Also noticed something, It can build boost sitting in my driveway with the clutch in, about 3psi.

NissanDiesel Forums

Tuning with turbo (SD22 / '85 kc 4x4)

Tuning with turbo (SD22 / '85 kc 4x4)

Re: Tuning with turbo

Who is online