Turbo or Squirt first?

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Gregetter
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Turbo or Squirt first?

Post by Gregetter »

Hi. I'm about to pull the trigger on switching over to MS3X on my LT4 383 with Hot Cam. I also have a turbo waiting to be installed. The engine is a proven runner. How would you guys advise me to proceed. Install the turbo then switch to MS3 or make the switch to Squirt before installing the turbo? (currently using the stock PCM with a tune but cannot retune it for turbo)

As a complete noob, it seems to me that I might as well install the turbo, switch to MS3X and start the setup and tuning process. If I switch to the Squirt, get it running, then install the turbo, seems like I'd have to go through the process of tuning twice instead of just "once" with the turbo installed first.

This motor is installed in an '83 280ZX and is used strictly for one mile top speed events, Texas Mile, Colorado Mile etc.
Drivability is not a big issue but good manners are always nice.
Thanks in advance.
Laminar
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Re: Turbo or Squirt first?

Post by Laminar »

If you set up the MegaSquirt first, you can scale all of your tables to accept boost, but tune everything in the off-boost range first. Then when your turbo is installed, you know you have startup and warmup dialed in, and you can get out on the street and drive normally to start dialing in boost.

Adding the turbo first piles on an extra layer of complexity on top of just getting the car starting and driving down the road.
Gregetter
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Re: Turbo or Squirt first?

Post by Gregetter »

Thanks, Laminar.
However, wouldn't the start, idle and warmup tuning be the same regardless of whether there is a turbo installed or not?
Remember that this is a track only car and driving around on the street is going to be problematic. So, I'll have to find a place, runway, to do test runs so I'd rather do the development all at once.
Donny
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Re: Turbo or Squirt first?

Post by lotus23C »

Can be hard trying to do it all at once, some problems hide other problems and you end up chasing your tail
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Gregetter
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Re: Turbo or Squirt first?

Post by Gregetter »

Good point. Thanks to both of you for the insight.
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Re: Turbo or Squirt first?

Post by suberimakuri »

As above. Squirt first mate.
Do all warm up, etc, and every where in map you can get to in idle. Also light accel enrichment in neutral
Scale rest of map based on this.
Check datalog of it running and all sensors etc.

Then turbo. :)
Gregetter
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Re: Turbo or Squirt first?

Post by Gregetter »

Picking up a really old thread here.
I did get the car running with MS3X controlling spark only and GM controller operating fuel. I got it running well enough to go 185MPH in the standing mile at the Texas Mile using a 100 shot of nitrous.
Then had to take a couple of years off, as did we all!!
But that time wasn't wasted. I did some port work on the heads, installed better valve springs, installed MLS head gaskets, replumbed the PCV system to use external catch can only (no Pcv valve), installed 80 lb DEKA injectors, built turbo headers, installed turbo and the thousand things that go with that task.
All that is to say that the motor is the same as before, a known runner. HOWEVER, this is not to say that I didn't screw something up putting the motor back together. To that end, I've checked compression and it's fine. I've taken the throttle body to look in the intake plenum to make sure a rag didn't get sucked in, switched from the 80 lb injectors back to 24ish lb injectors that I was running before,
and finally, STARTED PULLING MY HAIR OUT
HELP!!
Regardless of what the AFR says, the thing is running FAT,FAT, FAT. You can't stand to be in the same open garage when it's running and the plugs are very sooty except for where fuel has washed the tips clean. I'll attach a photo if I can.
I've tried playing with the idle valve, idle VE and tried to double check my TS entries multiple times.
Oh, and forget trying to give it any throttle. You can see in the log where I tried to and am unsuccessful.
Thanks in advance for any help you can give me.

Tuner Studio MS v3.1.08 MS3 1.5.2
Attachments
24lb injector test.msq
(285.2 KiB) Downloaded 15 times
2022-06-05_17.36.26.mlg
(640.79 KiB) Downloaded 14 times
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IMG_3181 (2).JPG (530.8 KiB) Viewed 236 times
Gregetter
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Re: Turbo or Squirt first?

Post by Gregetter »

I saw a mistake in my post. There are probably more than this one but
MS3X v 3.1.08 :o :roll:
Six_Shooter
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Re: Turbo or Squirt first?

Post by Six_Shooter »

Have you calibrated the Wideband? What wideband controller are you using? Where is the wideband sensor installed?

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Gregetter
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Re: Turbo or Squirt first?

Post by Gregetter »

I calibrated the sensor before trying to start for the first time after installing the turbo. The Sensor is an Innovate MTXL with a Bosch sensor. The Bosch sensor is installed vertically in the exhaust just ahead of the turbo. I know that's not the ideal place for it but due to space constraints it makes the most sense for this install. I made sure to use a tall sensor bung so that the sensor is not directly in the flow of the hottest exhaust gas.
BTW, today, I reinstalled the PCV valve and hose to the normal port for it hoping that this "calibrated leak" would make the difference. Instead, it made no difference at all.
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Re: Turbo or Squirt first?

Post by jsmcortina »

Is the fuel pressure regulator connected to vac/boost ? What fuel pressure do you see at idle? (Should be 5-10psi below static)
Is your "cranking RPM" set correctly? In the log you keep dropping into cranking mode which causes lots of fuel to be injected, I suggest you set the "cranking RPM" to say 300 RPM.

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racingmini_mtl
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Re: Turbo or Squirt first?

Post by racingmini_mtl »

Gregetter wrote: Mon Jun 06, 2022 7:24 pm ...The Bosch sensor is installed vertically in the exhaust just ahead of the turbo...
You mean on the pressurized side? If that's the case, the issue is not only temperature but pressure. You will not get the correct AFR and that will vary depending on the exhaust pressure. You will get the correct value at stoic but anything higher or lower will be wrong and the higher the pressure, the worse it will be and the further away from stoic it is, the worse it will be.

In theory, it would be possible to correct the AFR reading with a measurement of the exhaust pressure but that would need to be done by the controller to have corresponding pressure and AFR measurements. Doing this with an external pressure sensor would not work because you have no control on when the pressure and AFR measurements are done or any averaging or other computing that is done.

So there is no way to correct for this variation which means you need to change the position of the sensor after the turbo where it won't be affected by this large pressure variation.

Jean
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Gregetter
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Re: Turbo or Squirt first?

Post by Gregetter »

Thanks, racingmini. I didn't know that pressure would affect EGO readings. I will work on getting it repositioned to the the outlet of the turbine.

BUT, for now when I'm just trying to figure out how to get the thing to idle, while the exhaust temperature and pressure shouldn't be very high, I'll leave it where it is, unless you think that it's causing issues wnere it is now.

I didn't include this info in my post but the turbo is a Borg Warner S400, 80-something millimeter so I would think that backpressure at idle would be minimal, right??
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