Dyno day with the 260Z

[LeonV]

Some may be interested in a bit of data that I collected yesterday.

Ran my Z on the dyno all day, testing various jetting and playing with timing (first with E12-80 and then with 123ignition dizzy). The goals of this project was to learn, as it was my first engine build, try different things even if they go against "conventional wisdom", and enjoy playing in the sandbox that is Z-cars.

Ran it on the Dynapack at Works Motorsports, where I used to work (no pun intended).

Steve aka Datsuncrush, the owner of my previous 260Z, came by for support and videography!

Basic engine specs are: flat-top L28 (0.5mm over), shaved and ported P90, Isky L6 grind cam (.540"/270*), 45DCOE with ported and matched manifold, and MSA 6-1 header with a nice and quiet 2.5" exhaust (resonator and Walker Quiet-Flow muffler) so I can hear those Webers sing.

However, I'd like to think the devil is in the detail! Using the OEM head gasket, compression is 11:1. Piston-to-head clearance is .017" (less than 0.5mm!), that's with .021" piston pop-out from the deck. Because of the excellent quench and combustion chamber of the P90, it runs on CA 91 pump gas with 34* of advance all-in! The cam wipe pattern is cheated over to the pivot edge of the rockers. The head was ported by Rebello along with the port-matched and pinned intake. Running Supertech undercut intake valves and OEM L28 non-turbo head bolts on Dave's recommendation.

Final jetting was 135/F11/110 (main/tube/air) but it leaves a lot to be desired. The F11 tube is a particularly poor performer in sidedrafts and causes dramatic lean-rich-lean swings (+- 2.5 AFR!) at WOT. I did my best to reduce that tendency by limiting the amount of air drawn into the tube (hence the 110 air jet). Unfortunately, I did not have other tubes on hand to play with. Venturis are 36mm.

I plan to correct the mixture and play with cam timing another day but the end result is a good baseline to start from!

The yellow line is with stainless steel mesh filters and red is no filter. They were worth ~6hp peak and 1-3lb-ft across the RPM band.

And of course, the required video:

Overall, I'm very happy with the results and the Z pulls like hell!

[madkaw]

Leon,

was the block surfaced at some time?

I'm surprised pushing the clearance that tight when a 1.25mm gasket would have still been good squish .

so looking forward to my 54/47 set up. 

[moelk]

Nice numbers!! Congrats!

I have 150/F16/160

main/tube/air.

Runs great but I haven't had it tuned properly on the dyno. First try on the dyno I went up from 155 to 160 (air) because it went a bit rich at the top end. Then we had some problems with the dyno equipment and had to stop. So at least I know it runs well but would like to do it again to play with timing and other things.

[Patcon]

It's surprising the mesh cost 5 HP. As a side note what kind of money does it cost to have Rebello do that kind of head work?

[LeonV]

21 hours ago, madkaw said:

Leon,

was the block surfaced at some time?

I'm surprised pushing the clearance that tight when a 1.25mm gasket would have still been good squish .

so looking forward to my 54/47 set up. 

Hi Steve, good question. We skimmed .004" off to deck if I remember correctly. Like I said, it was an experiment and one of the things I wanted to learn is how much piston-to-head clearance I can get away with. There is a lot of (conflicting) info out there but I think I remember reading Bryan Blake's old posts about him running really tight clearances. Seems it's working well so far!

Now get that L28 going, you won't regret it.  

21 hours ago, moelk said:

Nice numbers!! Congrats!

I have 150/F16/160

main/tube/air.

Runs great but I haven't had it tuned properly on the dyno. First try on the dyno I went up from 155 to 160 (air) because it went a bit rich at the top end. Then we had some problems with the dyno equipment and had to stop. So at least I know it runs well but would like to do it again to play with timing and other things.

Thanks Andreas! I was very happy with those numbers, considering my stock S2000 made 200whp on the same dyno and much less torque.

I was bummed because I didn't have a full set of other e-tubes to test out. I was about to put some F16s in to test but only had 4 on hand. Too bad about your dyno session, time to get back in there!

17 hours ago, Patcon said:

It's surprising the mesh cost 5 HP. As a side note what kind of money does it cost to have Rebello do that kind of head work?

Dave cut me a good deal, I paid $1500. I'm local so no shipping was involved. This was for a valve job (including guides and valves), head porting, manifold porting (including pinning the manifold), and assembly. I brought the head to him fully disassembled. Even if it had cost more it would be well worth it, IMO.  

[moelk]

 

2 hours ago, LeonV said:

 

Thanks Andreas! I was very happy with those numbers, considering my stock S2000 made 200whp on the same dyno and much less torque.

I was bummed because I didn't have a full set of other e-tubes to test out. I was about to put some F16s in to test but only had 4 on hand. Too bad about your dyno session, time to get back in there!

Well i put it on another dyno the week after but the guy who owned that shop don't mess with carbs and did not have much time so well at least I got some numbers. I have less cr than you (around 10) but I made 180whp/240nm with no porting done to the head (and the same mesh filters as yours). I'm happy with does numbers but will do a dyno tuning next spring.

[LeonV]

26 minutes ago, moelk said:

 

Well i put it on another dyno the week after but the guy who owned that shop don't mess with carbs and did not have much time so well at least I got some numbers. I have less cr than you (around 10) but I made 180whp/240nm with no porting done to the head (and the same mesh filters as yours). I'm happy with does numbers but will do a dyno tuning next spring.

Very nice, I bet it pulls great! 

[Chickenman]

Air cleaner material and shape can make a surprising difference to the fuel curve. We tested various air cleaner tops on 580 HP Pontiac 463 motor. 

Engine was baselined with a Moroso 14" drop base air cleaner with domed metal lid and 3" tall open element air filter.

We lost 6 RWHP switching from a 14" Moroso Domed metal lid to a K&N Extreme filter top. K&N filter top lost HP and Torque through out the upper range. Vaccuum secondaries also started opening 200 RPM later. Air entering through top of K&N lid was creating turbulence with air entering from sides of the open element filter.

K&N extreme filter top:

 

Moroso Filter Top:

 

Removing air filter all together picked up an additional 5 RWHP from Baseline results. A taller air filter, 4.5"  or 5", would likely have negated that loss, but hood clearance forced the use of only a 3" tall filter.

 

 

[Patcon]

4 hours ago, LeonV said:

Even if it had cost more it would be well worth it, IMO.  

I agree! On the next engine I build this is where I'll put my money just wanted some idea of what to expect.

[madkaw]

Not to be annoying , but are sure the Nissan gasket was 1mm ? I'm thinking a 1.25mm was used and your clearance is more like .022. Like you said , lots of misinformation out there , so wanted to be sure that's the case.

[LeonV]

3 hours ago, madkaw said:

Not to be annoying , but are sure the Nissan gasket was 1mm ? I'm thinking a 1.25mm was used and your clearance is more like .022. Like you said , lots of misinformation out there , so wanted to be sure that's the case.

You bring up a good point, Steve, and I can't give you the exact number because I got antsy and never measured compressed thickness of a new Nissan HG. However, here is some data I documented a few years ago from my build thread on HybridZ:

Quote

I used an indicator and a bracket attached to the head to get some relative measurements regarding gasket compression and piston-to-head clearance. The head was torqued down with a previously compressed Felpro gasket that Jim sent me. The indicator was then zeroed and all bolts loosened. The number on the indicator then represented how much the gasket was compressed.

 

The indicator showed .021". I measured the uncompressed gasket thickness as 1.5mm/.059", meaning compressed gasket thickness is .038" or .97mm. I also double-checked myself with the indicator by reinstalling the head but without the gasket. The indicator read .0385", so within .0005" of the calculated value.

...

Using the .038" compressed gasket thickness, I get piston-to-head clearance of .017". Yes, that is pretty dang close but I'll be using a Nissan HG in the final iteration so I'm hoping for another .004-.008" from that. I will, however, use the indicator to measure compressed thickness upon final assembly to be sure.

Like you say, maybe the Nissan HG compresses less so my piston-to-head clearance is possibly somewhere in the .017-.022" range.

[HuD 91gt]

I ran 0.021" over deck, with my pistons, and a 1mm mls gasket and the car ran, never hard though (has having guide issues). Eventually switched to .050 mls after reading Bryan Blake's post. Curious how yours works out.

Edited October 25, 2016 by HuD 91gt