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Dyno results L28 Blowthrough turbo


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This is my first experience with a turbo charged engine  and the L28 and i was really unsure as to what to expect as a point of reference the tuned 350 Z's were producing 304 to 307 hp.

 

71' 240 Z, L28 280ZX turbo 5 speed drivetrain, with a Holley 4150 blowthrough , intercooled hybrid turbo 10lbs of boost with an internal wastegate. MSD 6 BTM with a 5,500 rpm limiter, locked distributor, aeromotive boost ref fuel regulator. petronix ignition. 92 octane gas.

Had the car for a year, bought as an abandoned project after being in storage for many years. 

 

This was a test run to establish some sort of baseline figure, unfortunately the clutch was slipping badly under full load (smoke coming out of bellhousing, that's what happens when you teach a teenager to drive stick and SCCA autocross). It was a really hot day, my air intake is currently behind the radiator, and i had removed the turbo blanket to adjust wastegate linkage. Engine and oil temp 180. Engine runs rich at 11 to 1 off boost and 14 to 1 under full boost.

 

 

conal%2071%20240Z%20%20conal1msn.com_zps

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Definitely should have more. At 10lbs, you should be seeing 250HP depending on what turbo, what exhaust, and the tune. Stopping the pull at 5500RPM is DEFINITELY leaving power on the table, but if the clutch is slipping you know you've got work to do first.

 

It may have started slipping the clutch when you hit 200HP, after that it won't matter, the rest of your graph is meaningless.

 

Isn't it nice to find the limits of your driveline on the dyno?

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Video 

http://vid270.photobucket.com/albums/jj89/CelticRover/IMG_2765_zpstmxctahx.mp4

 

 A/F shows (AEM digital gauge) at idle 10 to 1, at cruise between 12 to 13 to 1, and under full boost 13 to 14 to 1. 

If I abruptly lift off gas under full boost A/F can briefly spike as high as 15.0 to 1 

 

Cylinder head is stamped P90a but does not have hydraulic lifters. The former owner said the engine had undergone some machine work at his uncle's machine shop, He was running 17-20lbs of boost and spent some time on a dyno setting up the Holley, I have the boost controller set to its lowest setting at 10 lbs for now.The distributer is locked and according to my timing light is set at 42 degrees. I have a MSD 6-BTM but not adjusted the timing retard.

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What intake are you using? Can you show pictures of the engine and your boost tubing in particular? Did you set it up yourself or have it done by a shop? Sorry for all the questions but it seems few and far between here for a blow thru setup like that and i will be building something similar with my atomic efi soon.

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 A/F shows (AEM digital gauge) at idle 10 to 1, at cruise between 12 to 13 to 1, and under full boost 13 to 14 to 1. 

If I abruptly lift off gas under full boost A/F can briefly spike as high as 15.0 to 1 

 

Cylinder head is stamped P90a but does not have hydraulic lifters. The former owner said the engine had undergone some machine work at his uncle's machine shop, He was running 17-20lbs of boost and spent some time on a dyno setting up the Holley, I have the boost controller set to its lowest setting at 10 lbs for now.The distributer is locked and according to my timing light is set at 42 degrees. I have a MSD 6-BTM but not adjusted the timing retard.

I've only been on the site a few years but even I can see that your numbers seem all wrong.  Way lean for a turbo, even lean for a performance NA.  Timing is completely off, actually probably impossible to be there, the engine wouldn't start.  Slipping clutch so you don't really know what power output is.  You should start from scratch and confirm things like TDC, measure cylinder pressure to get an idea of CR, adjust the carb for more fuel at the critical portions of the power curve.  Stuff like that.

 

Not sure you'll get a lot of advice with what you're reporting because the situation is probably incomprehensible for the guys who do turbo.

 

And, don't forget, dyno numbers can vary by dyno and operator.  Comparing numbers is pointless.

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10:1 idle is on the richer side, you should be able to adjust a holley to be better at idle. L's start to stumble real bad if it goes lower then 10, most AFR gauges don't even read in the low 10's.

 

12:1 is ok for cruising, still a tad on the rich side. As long as it isn't leaning out when you tip in from cruise you could go leaner, if it is, then 12:1 is an acceptable trade off for keeping the tip in nice and happy.

 

14:1 is not ok under full boost. That is pretty darn lean for boost without some other control mechanism installed.

 

15:1 if you lift off the gas abruptly is ok, in fact it could read even leaner really since you aren't under load, the engine shouldn't be under combustion, just spinning. 

 

The main problem here is the 14:1 under full boost. That is living quite dangerously. 

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Thanks for the input.and tuning recommendations, 

 

I wouldn't have got this far without HybridZ.

 

Just getting some baseline figures does feel good.

 

Before i start adjusting timing on my locked distributor , the clamp orientation shown in photo is not exactly factory and might have something to do with my timing readings of 42 degrees ? 

 

Engine starts easily when cold in California weather, idles at a steady 700rpm, can require finesse to start after the car has sat for 10-15 min (heat soak ?)  

I previously Checked timing marks do line up at TDC, ( having questions over the timing readings, ) Removed valve cover, checked valves on #1 closed and rotor lines up with #1 spark plug post.

IMG_2772_zpsutgzym62.jpg

 

Its always a challenge taking on a previous owners project, my goal was to see how well I can get this blowthrough set up to work, before moving on to the RB powered '73 240 Z. Future plans for the L28 would be switching to mega squirt once the '73 is running and driving. Before the slipping clutch (not helped by rolling the fenders and Toyo R888's 245/45/R16) 

 

Its an Arizona Z intake, but if i did not acquire the parts with the car I would not go the blowthrough route, especially after reading Maximum Boost. Intercooler piping was sourced from friends and online, I can't weld stainless steel , pipe was cut with the hose clamp method. Still need to move intake to in front of radiator.

IMG_2776_zpsicyktxbp.jpg

 

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Did you check that the timing tab on the timing cover lines with TDC mark on the damper when the engine is at TDC on cylinder #1? Just bolting the tab on the cover doesn't ensure this. You can use a piston stop to find exactly TDC.

 

As far as the timing adjustment, you may need to drop the oil pump and rotate the distributor shaft to get the timing adjustment correct. Are you using a locked L28 distributor?

 

You need to set the static timing. Rotate the engine so that that it is in the middle of the timing adjustment range you would like. So if you would like to adjust between 20 and 30 degrees, put the engine at 25. Then rotate the distributor so that it is in the middle of the adjustment range. Pull the distributor cap and verify that the rotor is pointing at the #1 plug wire in the cap. If it isn't, then you need to drop the oil pump and rotate the shaft in the correct  direction. You don't need to drop the pump all the way, just far enough that you can rotate the distributor shaft with a set of needle nose. You may have to do this a couple times before you get the rotor close. Then pull the rotor and look at the reluctor wheel, it should be aligned to the mag pickup. If not, then adjust the distributor so that it does. The start the engine and check the timing with a light and adjust dynamically.

Edited by z-ya
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Please do the checks for your timing and timing tab. Reset the distributor as was mentioned earlier. 42 degrees is way high when your in boost above 3,000rpm. Since your using a locked distributor I would set it to 17 - 20 degrees and leave it there.

 

Then work on your carb jetting. If your wideband is reading correctly you should be at the AFR's that were mentioned earlier also. 11-11.5 full boost  16.0- 14.0 cruising. 13.0 - 12.0 at idle.  We dont want to see you blow a headgasket.

Edited by dexter72
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Not wishing to blow my head gasket or worse.

I had the car inspected at

http://www.dtpprecisionrebuilding.com/page.php?Carb_Rebuilding_and_Tuning .

 

Seemed confident based on what i have so far that the carb can be rejetted, and if that doesn't cure the AFR's under boost, Ill go from vacuum secondaries and convert to a double pumper. 

 

But first,

a new clutch, considering the centerforce II clutch kit and of course realign the distributor drive.

 

 

The distributor is a D612-52  107, which i think was from the original engine.

 

IMG_2772_zpsutgzym62.jpg

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  • 1 month later...

Carefully checked engine timing. Rabbit ears on cam, rotor lined up #1 cylinder, TDC mark on crank pulley and pointer accurate verified with a TDC indicator.

 

Oil pump drive was aligned correctly. Distributor tang 11.20 offset towards front of engine.

 

The the second timing adjuster bolt on the  D612-52  107 is unsurprisingly beyond its range of adjustment.IMG_3003_zpsjiqjclbx.jpg 

 

 

 

 

Engine about to go back in.  delayed by Eastwood's distribution centre catching fire. http://www.eastwood.com/eastwood-s-2k-aerospray-ceramic-underhood-black.html.

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