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Old 11-17-2000, 08:57 AM   #1
Trey
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Cool Cobb Tuning 2.5L NA Build - Dyno Results [LONG]

Ok folks, I finally got a chance to dyno the NA-build car last night. Overall, I'm pleased with the results.

For the record, the NA Build car consists of:
NEW NA-Spec Camshaft (SOHC)
Stage 1 Cylinder Heads (10.5:1 CR)
ExtrudeHoned Intake Manifold
64mm Bored Throttle Body
Aluminum Flywheel
ACT Street Clutch Kit
Borla Headers
Stock Cats
Stromung Pipe and Single Tip Muffler
all controlled by the Haltech E6K Engine Management System

Here's the first dyno chart comparing HP curves of the STOCK car (GREEN), the STREET CAM run (RED) and now the NA BUILD run (BLUE).



Remember this is measuring HP to the wheels, not engine HP.

Stock HP: 128.1 SAE
Street Cam : 142.1 SAE
NA Build : 172.0 SAE

These are REAL numbers, but if you want to speculate engine HP, we can assume 128.1 RWHP = 165 Engine HP in which case 172.0 RWHP would equal 222 Engine HP. Again, this is just speculative HP claims. I'll leave you all to debate this issue.

Next graph is comparing the HP and TORQUE curves of the STREET CAM run (RED/MAROON) and the NA BUILD run (BLUE/DARK BLUE).


A few differences, the new run has a dip in the torque band at 4000 RPM compared to a peak with the old run. This is due to the lack of the stock intake plenum. More on that later. Another key difference is how this new setup carries a flat torque band another 1000 RPMs after the stock one falls away. This can attribute to our gain in HP, though with a HP peak at 6000 RPM, we're hardly running a peaky, high strung motor. I'd have NO problem driving this car on the street every day and enjoying every minute of it. You don't have to rev it out to make the power, but it does pull to 6500 RPM quite nicely.
I set my rev limiter to 7500 RPM but we were getting valve float around 7100-7200 RPM so we never revved it out past that. With these cams, you could likely run a safe 6800 RPM redline. BTW, these engines sound MEAN above 6500 RPM. WOW!

So there you have it. A completely streetable motor that drives and idles great and produces 172 and 160 ft-lbs of torque to the wheels. Throw in our speculative engine HP calculations and we have 222HP @ 6000 RPM and 206 ft-lbs from 4500 to 5600 RPM. (Bring it on WRX! )

If anyone's interested, we are selling this engine as a whole, as it stands, fully dyno tuned with the Haltech E6K. Please inquire privately.

Regards,
Trey
CobbTuning.com
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Old 11-17-2000, 09:08 AM   #2
Memnoch
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GOD DAMN
Trey you should move to Puerto Rico!!
Da-da-damn!
It sucks living in here folks, everyone and their dog should take their RS to Cobb right now

Am I right assuming this would work with a turbo? Since we're not raising the compression..
Only the piping would have to be changed because of the t-body right?
Oh and the headers...hm...

[This message has been edited by Memnoch (edited November 17, 2000).]
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Old 11-17-2000, 09:26 AM   #3
Kevin Thomas
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Cool

Wow! This is great Trey. If the WRX coming to the U.S. has hp in the 210-220 range, your N/A motor would be right there with it. Incredible! Now, I wonder how many people are going to go this route.

Thanks for FINALLY doing an N/A build-up and showing us what potential the 2.5RS's engine has. Im impressed!

Now it's time for you to tirelessly get working on that autotranny mod. I have the $$ ready for one. Just say it's ready. Hehe!

[This message has been edited by Kevin Thomas (edited November 17, 2000).]
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Old 11-17-2000, 09:33 AM   #4
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Actually I thought about it and why would I want to turbo an RS having those mods? I'd leave it just like it is, all N/A. And I just checked and yes compression has raised. I thought that 10.3:1 was the stock one. It's 10.1:1. Oh well, I don't care. I'd sign up right now if I could

I'm going to save up for it just in case that by some chance those things could be done to my car(Puerto Rico ).

Great job Trey!!

[This message has been edited by Memnoch (edited November 17, 2000).]
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Old 11-17-2000, 09:41 AM   #5
STiShawn
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Trey for president! Your are awesome. As soon as I can afford heads/cams and and ES (tecll or yours) I'm allllll over it. Sounds like the RS just got even more fun. Now, do you think a well built NA RS can take a new WRX?

[This message has been edited by STiShawn (edited November 17, 2000).]
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Old 11-17-2000, 09:45 AM   #6
stimpy
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Thats nothing short of amazing: 44rwhp increase above stock!! Do I dare inquire as to what the price of that is altogether? Guess I need to rethink my turbo vs na thoughts. That reminds me, I need to call you about those cams I ordered.

Do you have any idea on emissions numbers? I am curious if emissions will be a problem with this na setup.

Good job Trey.

Still a happy Subaru owner,

Jon
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Old 11-17-2000, 09:48 AM   #7
Memnoch
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I think if we took that 222hp figure then it could be done. Since our cars are lighter too. And I don't think drag would be that much of an issue in the 0-60 run. Assuming the new WRX doesn't have as much drag as we do of course. And then gearing, and and..argh n/m, who knows?


[This message has been edited by Memnoch (edited November 17, 2000).]
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Old 11-17-2000, 09:50 AM   #8
TR
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Trey, do you have any plans for the Haltech? is a Haltech kit in the future?
thanks...
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Old 11-17-2000, 10:03 AM   #9
HamFist
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That is very imprezzive . When are you going to try 11.5:1 pistons, high flow cats, and stack injection with that combo?
Hehehe...275? 300? Can ya smell it?

Gary
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Old 11-17-2000, 10:05 AM   #10
edekker
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Trey,

That's fantastic!

If that indeed extrapolates to 222Hp at the crank, then we're talking 310HP when supercharged with my Eaton blower (40% increase) assuming it's Haltech'ed with bigger injectors right?

I've got some big-time thinking to do...

Ed.
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Old 11-17-2000, 10:11 AM   #11
ColinL
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Now think about what it might be with equal length headers and a single straight 3way catalyst...

Impressive results. Quarter mile times of said car would be cool, assuming the motor has not been pulled yet.
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Old 11-17-2000, 10:50 AM   #12
Catfish
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Great job Trey.

Finally, proof of the N/A potential. It has always been my assumption that the stock cams were severely limiting this engine's potential, and now it's been proven. Still, those are impressive gains. I wouldn't have thought we'd see that much improvement.

In regards to the Haltech, care to elaborate? Does it use the stock coils, thus making it a truly 'secret' black box?

Cheers,
Dave
'00 Subaru 2.5RS Sedan
'00 VW Passat GLS 4Motion
'72 Datsun 240Z

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Old 11-17-2000, 11:24 AM   #13
STiShawn
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I was gonna but a WRX wagon, not any more. I just got a stromuung with intermeditate pipe, and an ISR intake, now I just need to order all of Trey's parts and I'm golden. There is a nasty little DSM that likes to humiliate me around here......look out!
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Old 11-17-2000, 11:28 AM   #14
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WOW!

I think Shiv's first turbo project writeup was doing 183hp at the wheels on a 4 wheel dyno (April, May or June 2000?).

Larry
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Old 11-17-2000, 01:14 PM   #15
cakagan
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Sounds great, Trey! But, um, what about those of us with the DOHC 2.5 RS?

Thanks,
-Chris
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Old 11-17-2000, 01:56 PM   #16
boxerman
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Great work Trey,
I have to say that I feel somewhat vindicated as should all of those who were talking about NA build ups 8 months ago. At the time there were so many naysayers, those who said the motor wouldn't hold past 6500rpm without spitting rods, those who said the cam won't work with the ecu (I know this is a Haltech, but others are running the cams with the stock ECU), those who said you couldn't get that much power without a v-tec, those who said that the hydraulic lifters would prevent high rpms, stretched motor, open deck, grenade etc, etc.

We don't need no steenkin turbos.
Thanks Trey.
Tim

BTW how much would all of this cost. Are you considering a full top end kit (heads, cams, throttle body, intake and exhaust)
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Old 11-17-2000, 02:05 PM   #17
RageHardIntoTheBendies
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I would be interested to know how that setup would work without the headwork, or would the heads be too much of a bottle neck then?
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Old 11-17-2000, 02:13 PM   #18
Trey
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Imprezer - One thing I noticed on the dyno was that during the little "dip" in torque, the manifold pressures were going nuts. With the MAP sensor connected to the center plenum section of the intake manifold, with no other connections, it's normal for it to see variations of 1" or so in the pressure. During the RPM's that the dip occurs though, it has as much as 3-5" of vacuum variation differences. I believe that's due to internal frequency resonating inside the intake manifold at that RPM point. It's possible that building that little cross-over tube can help buffer out some of these frequencies and smooth out the air. When the air in the intake manifold is bouncing around like that, air speed is reduced and power (torque) goes down. After 4500 RPM, the air speed is regained and power picks back up. That's an interesting idea, though, I'd assume it works.

I also noticed it has a different center plenum chamber? They get rid of the bend down the intake manifold takes before it goes into the center chamber. That's worth some HP right there!! Can't see it too well. Would like to see a scan of that too!

As for the bulge in the intake tube itself, leading to the throttle body, I tried that and it didn't help as much as I had hoped. I was able to build more torque below 3000 RPM, but it didn't smooth out the subtle dip @ 4000 RPM. Maybe that FLATT guys found that out as well and ended up building the cross-over tubes as the next attempt to fix the problem.

I know I'll stir up the hornet's nest with this one but I wouldn't be surprised if there's another 15-20 HP left to be gained in the intake manifold. I could be wrong, but I still think the engine is running out of air. I'd be willing to develop an intake manifold for someone, but I'm not looking to build one for my own use right now.

As for DOHC parts, they're coming. We wanted to finish this SOHC project first. My next project will most likely utilize the DOHC head so I'll probably be building quite a few parts for it very soon, beyond those that are already in the works (ie: cams).

Regards,
Trey
CobbTuning.com
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Old 11-17-2000, 02:25 PM   #19
Bassem
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Imprezer, Trey, it would be interesting for you to guess how long that crossover tube is. You can then see what rpm it can set up a standing wave at to ensure that it maximizes mass flow to the intake valves.

Just a suggestion if anyone wishes to pursue it.

good job Trey

Bassem
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Old 11-17-2000, 04:21 PM   #20
copec
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trey, what altitude is that? Are those numbers currected from altitude?

Doesn't the dyno do that automatically?

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Old 11-17-2000, 06:43 PM   #21
Turk
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Let me get this straight, you got those hp numbers without an intake? An intake wasn't on the list, that could be around (more or less) another 10hp! Great Job Trey keep up the work!

Turk
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Old 11-17-2000, 08:41 PM   #22
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I remember some Yamaha 4-cyl motorcycle engines had balance pipes between intake tracts. But, they set them up on cylinders that were 360deg out of phase. This way, the gas that's been brought up to speed has somewhere useful to go when the intake valve gets slammed shut, into the other intake. These were installed on bikes that had pretty bad flat-spots in the midrange. YEIS they called it.
The FLATT pipes must do something different as the pairs are at 180deg and the timing of the 'boost' flow is wrong. Maybe they work like a boost-bottle on a 2-stroke?
To get the YEIS effect, you'd have to balance the cylinders at opposite corners of the motor.

Good work Trey, but when we gonna get some 1.8 cams then?, gnash, weep..!
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Old 11-17-2000, 09:08 PM   #23
shiv
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Trey writes...

"These are REAL numbers, but if you want to speculate engine HP, we can assume 128.1 RWHP = 165 Engine HP in which case 172.0 RWHP would equal 222 Engine HP. Again, this is just speculative HP claims. I'll leave you all to debate this issue."

Great results any way you look at it Trey! But (here comes the debate part why are you speculating a fixed percentage drivetrain loss? This results in inflated numbers. How does a 44 hp gain at the wheels result in a 57hp drivetrain loss? That's a lot of loss to blame on a drivetrain, awd system or not. Esp. if you converted over to rwd. Most reasonable people suspect drivetain loss stays pretty close to constant when dealing with non-obsene power gains. So, 165-128=37 drivetrain loss. That being the case, 172 wheel hp+37 drivetrain loss equals 209 flywheel hp, which is probably the more accurate estimate of the engine horsepower. Still, great results!

Case in point: last year's UPRD dyno results showed 95 wheel hp (stock) vs. 183 wheel horsepower (with a stock 7psi Minnam turbo). 93% gain. Following your correction method, the car would have made 320 horsepower (165x1.93), which obviously, isn't possible consider the low boost and state of tune. More likely is that it gained 183-95=88hp. And 88hp+165hp=253hp which is much more reasonable.

Another example of where the fixed percent drivetrain loss example falls short is when one sees the results of SCC's intake and exhaust tests. Did our car really make 196 flywheel horsepower with just an intake? And 205 flywheel horsepower with just and intake and exhaust? Hmm... probably not

Shiv

[This message has been edited by shiv (edited November 17, 2000).]
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Old 11-17-2000, 10:23 PM   #24
XT6Wagon
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May I make a suggestion? When you offer the "hot" cams instead of the street cams you could include stiffer valve springs in the package, thus forcing anyone who wants the cams alone to recognise the valve float problems at high RPMs. The SHOSHOP did this for years on thier lumpy cams as the higher lift was killing the stock springs.

If you think 7K sounds great just wait for 8K.....
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Old 11-18-2000, 12:08 AM   #25
ColinL
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Exclamation

Whoa there Larry, don't even attempt to compare the two dyno results. No sound logical conclusion can be made because the tests are so very different... RWD dynojet vs. AWD Clayton.
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