Alright, here are some results from today's dyno testing. I don't have the dyno files yet, since Hydrazine's floppy disk got corrupted, so he'll have to call the dyno shop on Monday. So I can only go off my memory for the peak numbers. We'll have nice Excel plots in the future.

We also ran into another issue with the threads on my lower plenum starting to strip. The plenum's aluminum is fairly soft, and I have already disassembled/installed the top plenum several times. Since the car's my daily driver, I became concerned that if more threads became stripped with more disassembling/assembling, that I wouldn't even be able to get to work come Monday. So we could only do two test configurations today. One with Crawford V5, and one with a stock plenum with spacer. We did 2-3 runs in every configuration, and the results were always within 2 horsepower, so the results are fairly reliable.

Let me start by giving some background info on the car. It's a 5AT G35 coupe 2003.5. I've done 4 dyno sessions now.

Dyno Day #1, this was at Strictly Dyno in Reseda on a dynojet. The car only had a Z-tube at the time. In 4th gear it got:
219 WHP

Dyno Day #2, also on the same dynojet. This time it had Kinetix V3 plenum, UR crank pulley, popcharger, in addition to the Z-tube. Again in 4th gear:
223 WHP

Dyno Day #3, this was on the dynapack at Church Automotive. The results are summarized on this page
dyno day #3
and it's in the winter edition of Sport Z Magazine. The dynapack is known to give higher numbers, since the wheels are taken off the car for testing. THX723 was at Dyno Day #2 and #3. He got 240 WHP on Dyno Day #2, and with the same mods ran 251 AHP (axel horsepower) on Church Automotive's dynapack.

My car was the only automatic that ran 4th gear (1:1) that day, everyone else was in 3rd. The MT's were in 4th. My mods at that time were: Crawford V5 plenum, popcharger, Z-tube, UR crank pulley, and some polish work on the lower plenum, intake manifold, and throttle body. The results are published, but just to rehash, it ran:
254 AHP

Dyno Day #4 (today)
I had done more polishing to the lower plenum. I also changed out my rear brakes from the stock 5AT ones to the OEM 2 piston Brembo calipers with 2-piece stoptech rotors. The stoptechs weigh about 2 lbs more than the stock 5AT rotors (13 lbs vs 11 lbs respectively).

The first runs (Crawford V5) were in 4th gear, just to compare to dyno day #3's results:
259 AHP .....a gain of about 5 HP. Not bad, considering there's not much left to polish, and I'm running slightly heavier rear rotors now.

We then did 3rd gear runs:
269 AHP .... 3rd gear was about 10 AHP higher across the board from 4K RPM and up. So my car compared to the results on Dyno Day #3 is pretty good now. Again, it's got a completely stock exhaust system, stock ECU.

Now we changed out the Crawford V5 and put on a stock plenum with 1/4" spacer.
In 4th gear: 260 AHP
In 3rd gear: 275 AHP
In comparison to the Crawford, it basically gives 5 AHP from 6K RPM to peak at 6.3K RPM. At lower RPMS, it's basically identicle.



Summary:
I know that we need more data, but the stripped threads put a wrench in our plans. What's probably going on, is that the spacer helps by changing where the air is directed coming from the plenum's neck. In stock form, the air is directed at the "hills" on the lower plenum. With a spacer, the air flows above those hills, and has a less restricted path. I'm now running the Crawford with a 1/4 spacer. There's no clearance problems on the coupe with this configuration. What I'd like to do is get the car back on the dyno in this config, but I have to fix the stripped threads first.


When I say "hills" I mean the raised portions near the middle of the plenum where the air first goes when it enters the plenum space.

 

Concerning the stripped manifold bolts, are you guys using the factory spec torque? I'm constantly reading about guys tightening these bolts "as tight as they'll go" which could lead to big problems. I know the intake manifold bolts on the Maxima only needed 12-18 ft/lbs which is basically nothing. Over torquing them leads to gasket leaks, stripped bolts, and stripped threads. I'd imagine that the G35's bolts only need about 15-20 ft/lbs.

As for measuring the power gains, I can't stress how imporant it is to dyno on the same machine everytime, otherwise it' just waste of your time and money.

Dynopaks are brake-dynos which means you can influence the numbers by simply loading/unloading the dyno brake. This can lead to inconsistent dyno numbers and lots of bias. Brake dynos are great for tuning your car in race type situations because of the load they can exert, but they make for poor measuring devices for smaller gains. The Dynojet is far better for just measuring gains.

 

Well, I'm still pretty cranked to see the dyno charts and compare the curves.

 

Just remember that Dynopaks typically will show a higher peak power at a higher RPM.

Example:

G35 sedan with mods, no changes between dynos

Dynojet 220whp@6000rpms
Dynopak 245whp@6300rpms

The problem is that you can't compare these dynos at all. It would be utterly meaningless.

 

About the stripped threads... I'd recommend drilling and taping the holes to the appropriate size and installing a Stainless Steel Insert. An insert is a threaded ID and OD plug that allows you to fix, stripped threaded holes. Also, get the free running inserts (don't get the locking type if you're ever planning on removing the plenum again). Simply (and carefully) apply a little loctite to the OD of the insert before screwing it into the lower manifold and insert it flush to .030" below the flanged manifold surface.

 

Right. Just compare the dyno curves (and A/F) between the dynopak runs on the same or similar days.

 

Agreed, that's what I had tried to do with my first 3 dyno days.


Even with the same dyno machine, it can be tricky. My first two dynos were on the same machine in Reseda, CA. All the 350z's thought that the HP from the second day was 8-9% lower than it should have been. So that's why I usually only dyno with other g35s and 350zs on dyno days. At least I can tell how my car compares to those cars on that day. Otherwise, the absolute numbers don't mean much.

Anyway, just to clarify, when I say Dyno Day #1, 2, 3, and 4, these are all on different days.

#1 was on 2/7/04 at Strictly Dyno in Reseda, CA

#2 was at 6/12/04 at Strictly Dyno again

#3 was on 9/4/04 at Church Automotive

#4 was 2 days ago at Church Automotive.

 

Here is the dyno graph.





There are 6 runs here. 3 with the Crawford V5, and another 3 with the stock plenum/spacer. I put all of these runs on the same plot so that it's obvious that I'm not just choosing the best of one config vs the worse of the other. (there's actually a 4th Crawford run, which was the same as the other 3, but the plot is already busy enough). I also have the torque from the first Crawford run vs the first stock plenum/spacer run, just to give people an idea of how the torque curves look.

All of these runs were done in 3rd gear. And again, this is on a dynapack, and we expect the absolute numbers to be higher than a dynojet.

You can see the consistency in the gains above 6K RPM. These runs were done within 30-45 minutes of each other, and the car's axles were left connected to the dynapack when we switched parts.

 

not to sound off.. but where can I get that spacer...?

 

E_K, Tony,

Awesome work.... I'd love to get one of these...especially if they are made of some heat insulating plastic...

G

 

Hi Gurgen,

The insulators are comming really soon. I need to finish testing on my car first. The insulator isolates both the upper and lower plenum from heat soak.

 

Good job on the spacer. Did you car still sound stock or did it have the sound the crawford and kinetix makes? How much do think the spacer will be if you can say?

 

Nice.....

So do you still want to test this on my FI car? I figure once I have a good tune on mine, it would be really interesting to see what the spacer will do.

Are you planning to only make 1/4" spacers only, or will you try 1/2" and 3/4" versions as well?

Again, Tony, VERY VERY nice work.

Gurgen

 

Definitly! Your car should make a really good data point for worst case boost pressure!

It would be interesting to see how it would do on the dyno too.

The 1/4" is more specific to the Z to allow the strut bar.
The 3/8" is more specific to the G to allow the engine cover.
The 1/2" fits the 350Z engine cover on any car. But no strut bars or G35 engine covers though.

I found on my car that the 3/4" spacer just BARELY fits. It should do the same on yours too.

And they sound really cool too. The larger the spacer, the deeper the growl from under the hood.


Tony

 

wow. 3/4 inch spacer? is there a point at which it would be bad to keep increasing size? should i just get the 3/4 inch or go with a v5 + 1/4 inch or 1/2 inch?