# Turbo issues



## aminidab (Apr 30, 2002)

My turbo setup is the HS GA61DE kit, GT28RS, 370cc injectors/240sx MAF and a JWT ECU. I'm having a couple issues with my setup that I'm trying to work out.

I have had my timing set at 10, but I noticed I was getting a little bit of pinging around 11 PSI. I hooked up a multimeter and tapped into my MAF signal wire to check the voltage. I was hitting a max of around 4.8 volts, so I figure that I'm not maxxing out the MAF or the injectors ( assuming the 370cc injectors max out around the same time as the S14 MAF )

The EGTs aren't overly high, I figure I should be able to run at least a little above 11 PSI on 93 octane without detonation as it dosen't look like I'm leaning out(EGTs and MAF voltage).
I'm getting the pinging again at around 11 PSI, regardless of RPMs. If I hit that boost level at 5K or 7K, I hear a little pinging. This is in 3rd and 4th gear.

So I knocked the timing down to 8, and I was able to run a little bit more boost, up to around 12 PSI without pinging.
At this point the MAF voltage is getting to ~4.95. I realize at this point I'm getting close to maxxing out the MAF or injectors, but the question is why did I have to knock down the timing to get there?

It would be nice if I had a wideband O2 so I could figure out what's going on with the air/fuel ratio, but I don't. I'm thinking of getting it dynoed soon, to get a better idea of what's going on here and see what kinda #'s I'm making.

Also another problem I'm having... running rich. The car is running pretty rich, enough to make my bumper black. The gas mileage is still pretty good though ~28 MPG. I've checked/adjusted TPS, timing, spark plug gap and pressure tested my piping. I do have a small leak at the compressor outlet I haven't been able to completely get rid of but other than that everything is set correctly.
Any suggestions on other things to check or what could be causing the rich condition?


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## chimmike (Oct 17, 2002)

what is the plug gap set to anyways?


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## aminidab (Apr 30, 2002)

chimmike said:


> what is the plug gap set to anyways?


I've tried various gap sizes from .020 to .035, but currently it's set to .030.


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## chimmike (Oct 17, 2002)

sounds good. .035" is too far apart. I stick between .025 and .030 myself.


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## aminidab (Apr 30, 2002)

chimmike said:


> sounds good. .035" is too far apart. I stick between .025 and .030 myself.


Yeah, I had break up at .035. I found I could run as high as .032 without breakup, but I figured there was no reason to run those close to the limit. That's why I settled on .030.


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## wes (Apr 30, 2002)

Are you sure its detonating? How do your plugs look and what are your EGT's at that RPM? I agree that you should get it on a dyno/wideband to see what is going on with the AF ratio... And do you still have the 2.5" exhaust? 

At any rate my car has been running great thus far with the new setup granted I am using a different MAF and injector's than you are. I am running 6 range plugs at .025 gap and 8 degrees of timing.


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## aminidab (Apr 30, 2002)

wes said:


> Are you sure its detonating? How do your plugs look and what are your EGT's at that RPM? I agree that you should get it on a dyno/wideband to see what is going on with the AF ratio... And do you still have the 2.5" exhaust?
> 
> At any rate my car has been running great thus far with the new setup granted I am using a different MAF and injector's than you are. I am running 6 range plugs at .025 gap and 8 degrees of timing.


Not 100% sure it's detonating. Since the noise that I believe to be pinging didn't occur until 12 PSI vs 11 PSI when I reduced the timing, it makes me believe even more than it's pinging.
I don't have anything recorded as far as EGTs, but I'll see if I can post some data in the next day or so. Nope I have a 3" cat-back on there, the DP is 2.5" though. I'm starting to seriously think about putting a 3" high flow cat on there, it could only help lower the EGTs. I'd prefer to get everything tuned as good as possible before being on the dyno.. but at the same time I think it could help me fix some of these issues.

When I've pulled the plugs there are a whitish tan color.

Glad to hear your new setup is running good, did JWT recommend setting the timing at 8 or 10 degrees with that setup? I'm definately looking forward to reading all about it.


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## wes (Apr 30, 2002)

aminidab said:


> Not 100% sure it's detonating. Since the noise that I believe to be pinging didn't occur until 12 PSI vs 11 PSI when I reduced the timing, it makes me believe even more than it's pinging.
> I don't have anything recorded as far as EGTs, but I'll see if I can post some data in the next day or so. Nope I have a 3" cat-back on there, the DP is 2.5" though. I'm starting to seriously think about putting a 3" high flow cat on there, it could only help lower the EGTs. I'd prefer to get everything tuned as good as possible before being on the dyno.. but at the same time I think it could help me fix some of these issues.
> 
> When I've pulled the plugs there are a whitish tan color.
> ...



Typically your plugs will be white with speckles on them if your detonating. Not to say your not, just another way to check... I am still running my stock cat and am thinking about experimenting with a stocker/high flow/ and test pipe to check EGT's and power. I wouldn't run the test pipe on the street but figured it'd be good for comparison... 

They did not recommend it I just figured I'd be conservative since I just got the car running and no one has ran this setup before.


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## Zen31ZR (Mar 24, 2004)

aminidab said:


> . I'm starting to seriously think about putting a 3" high flow cat on there, it could only help lower the EGTs.


 Only out of the tailpipe. What matters is EGT right as the exhaust exits the head. Where is your probe tapped.......


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## wes (Apr 30, 2002)

♣Zen31ZR♣ said:


> Only out of the tailpipe. What matters is EGT right as the exhaust exits the head. Where is your probe tapped.......


He is tapped in the #3 runner. What he is getting at is that if the OEM cat is going and or has melted then it can create excessive back pressur ewhich in turn could drive up EGT's regardless of where the probe is placed.


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## aminidab (Apr 30, 2002)

wes said:


> He is tapped in the #3 runner. What he is getting at is that if the OEM cat is going and or has melted then it can create excessive back pressur ewhich in turn could drive up EGT's regardless of where the probe is placed.


yup exactly. Removing any exhaust restirction can only help lower the EGTs, as it reduces backpressure. When I switched from a 2" mandrel bent catback to a 3" one I noticed a big difference in EGTs. It's not so much that the peak EGTs were lower, but they dropped much quicker when off boost and were lower when crusing.

Did some tests with the EGTs as I hit full boost.
In third gear as I hit 12 PSI, EGTs are at about 1350-1400. They continue to climb if I stay at that boost level, they briefly hit 1550 one time when I took 3rd gear to redline. I was watching the MAF voltage on the same run and it peaked at about 4.9.


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## Zen31ZR (Mar 24, 2004)

I would think at that point the turbo is already providing all the backpressure the system will ever see, unless the cat is completely clogged. The most backpressure the system will see with the cat as the problem will be right at the turbine exit to the downpipe..... 
Sorry, not trying to be argumentative.  

However, those EGTs are quite high. Maintained, that could cause problems. I don't think a different sized cat will help that much, and as you said won't affect peak EGT that much. As I recall, 1590 is right about where things start melting. Unless you're at a point where you have to run on the ragged edge to make more power, I'd back off of that a bit, you'll only damage the engine over time......


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## aminidab (Apr 30, 2002)

♣Zen31ZR♣ said:


> I would think at that point the turbo is already providing all the backpressure the system will ever see, unless the cat is completely clogged. The most backpressure the system will see with the cat as the problem will be right at the turbine exit to the downpipe.....
> Sorry, not trying to be argumentative.


Well I could argue about the how/why I think a less restrictive exhaust would result in lower EGTs but really I only have theories about that, nothing solid. Maybe someone will chime in about that. Point is after installing a less restrictive exhaust, I had lower EGT's on my setup.



> However, those EGTs are quite high. Maintained, that could cause problems. I don't think a different sized cat will help that much, and as you said won't affect peak EGT that much. As I recall, 1590 is right about where things start melting. Unless you're at a point where you have to run on the ragged edge to make more power, I'd back off of that a bit, you'll only damage the engine over time......


Here I agree with you, 1550 is quite high. Keep in mind that was only for a second or two. Usually I don't let my EGTs get over 1400, 1450 tops.
A different sized cat may not have a major affect if the current cat is functioning fine, but if it's melted or clogged it could.


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## dburone (Apr 2, 2004)

What is your compression ratio?


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## himbo (Sep 20, 2003)

also, shouldn't you reset the timing, as the JWT ECU automatically advances it?


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## aminidab (Apr 30, 2002)

dburone said:


> What is your compression ratio?


The compression ratio is stock, which I believe is 9.9:1. The JWT ECU advances/retards the timing from the base timing. So lowering the base timing will lower the timing overall regardless of what the ECU is doing.


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## velardejose (Sep 9, 2004)

A pinging scenario with rich mixture would colour the spark plugs black with the electrode tips white, with or without white speckles


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## himbo (Sep 20, 2003)

i thought the compression ratio on the GA16DE's is 9.5:1


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## aminidab (Apr 30, 2002)

I found that info by a search, there seems to be a debate about if it's 9.5:1 or 9.9:1. I also did a quick search in the FSM but didn't turn up anything.


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## James (Apr 29, 2002)

i think 95+ 96's are 9.5, and after that it was 9.9... I remember that one guy's website that actually tested it to be like 9.59 or something...


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## javierb14 (Jul 9, 2002)

throw it on a dyno and tune it from there. you can adjust your values and read the trq output of the motor....the trq curve will tell you if its detonating. 

the plugs will also tell you if its detonating, but you have to view them at that time. basically, you can do a WOT pass on the dyno and cut the ignition. the plugs will show exactly what was going on up to the point when you turn off the motor. you dont want to wait and let the motor idle down, cool, and then check the plugs since then you would be viewing what happens at idle conditions. its best to do this method on a dyno....if you do this on the street, you lose power brakes and you dont want to lock the steering wheel.

this is an excellent course if you are interested in learning more about tuning 
http://www.efi101.com/efi101.html


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## aminidab (Apr 30, 2002)

javierb14 said:


> throw it on a dyno and tune it from there. you can adjust your values and read the trq output of the motor....the trq curve will tell you if its detonating.
> 
> the plugs will also tell you if its detonating, but you have to view them at that time. basically, you can do a WOT pass on the dyno and cut the ignition. the plugs will show exactly what was going on up to the point when you turn off the motor. you dont want to wait and let the motor idle down, cool, and then check the plugs since then you would be viewing what happens at idle conditions. its best to do this method on a dyno....if you do this on the street, you lose power brakes and you dont want to lock the steering wheel.
> 
> ...


I'm going to get it dynoed on thurs. My plan right now is to do 2 or 3 runs.. 1 at 8 degrees timing, 1 at 10 degrees, both at 11 PSI, then depending on how that goes maybe 10 degrees timing at 12 PSI.
Since I have a JWT ECU, there isn't too much tuning I can really do, only adjusting the base timing and boost level.
I'll try pulling one of the plugs right after a run(especially if I suspect it's detonating) I can't think of a better time to do it.

Thanks for the info, I'll post the results later in the week.

That course definately sounds interesting, if only I could figure out a way to get my company to pay for it :thumbup:


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## himbo (Sep 20, 2003)

aminidab said:


> I found that info by a search, there seems to be a debate about if it's 9.5:1 or 9.9:1. I also did a quick search in the FSM but didn't turn up anything.


search here, i know i've read that the compression ratio on the GA's is 9.5:1

also, i dont think they raised it after 96 because the hp and torque output the same (please correct me if i'm wrong)


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## velardejose (Sep 9, 2004)

You just cant stop your engine after boosting to see your spark plugs
Turbo has to cool down to avoid 'coking'


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## himbo (Sep 20, 2003)

velardejose said:


> You just cant stop your engine after boosting to see your spark plugs
> Turbo has to cool down to avoid 'coking'


righto... thats why turbo timers are used


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## javierb14 (Jul 9, 2002)

velardejose said:


> You just cant stop your engine after boosting to see your spark plugs
> Turbo has to cool down to avoid 'coking'


yes, you can and yes the possibility of coking is increased. this is just one tuning technique used to determine what is going on under max load.. your only going to do this a couple of times....then once its tuned you dont really have to do it anymore. its basically a trade off of what do you want to fail...the turbocharger or you motor? what is easier and or less expensive to replace? granted you can buy 3 or 4 stock GA16DE long blocks for the price of one disco potato...but thats not the case with a "built" motor  besides, the GT28RS like the other GT series turbos has a water cooled CHRA...its already running cooler than your standard bushing turbo.


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## velardejose (Sep 9, 2004)

Water cooled, good point
I started using that spark plug tuning method back in mid '80s in my dual weber vw bugs...
Now I prefer an O2 sensor, but occasionally look at the spark plugs
Almost black brown with white in the electrodes


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