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Old 09-05-2007, 03:52 PM   #1
Element Tuning
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Default Element STI 507 whp at 24 psi but what went wrong?

As funny as this may sound this is only the 3rd time our Time Attack STi has been on the dyno. Since we were using all off the shelf Element Tuning parts and a stock engine all that was ever really needed was a quick tune of the base map before heading off to the track. After a season on racing and over 15K miles on the stock motor we took our time and built an engine that would suit our needs. We built from the bottom up a custom engine based on our experience road racing utilizing custom 10:1 compression pistons, upgraded valve springs and Cosworth 278/274 camshafts. I was estimating something special at fairly low boost.

At 24 psi the car made 507 whp on a conservative tune of Sunoco 110 and water from the Hydramist system and with no AVCS. The basic power mods are Element Hydra EMS, Element GT65 Turbo Kit, Element Competition Catch Can, Element Hydramist, and Element Tuning Engine. Since this was our road race mapping I just wanted to see what it would do.



All the dyno runs were between 94 and 95 degrees Fahrenheit and within 2-5 hp so the engine and Hydra tuning were very consistent from run to run. Unfortunately the WG spring was much too soft for how my TurboSmart E-Boost was setup so on the dyno I couldn’t hold more than 24 psi so a stiffer WG spring is in order. With 30 psi power should peak around 580 whp with the same tuning strategy and likely about 20 whp more if I tuned it on straight VP C16. For stock heads with only camshafts this is exactly where it should be on this dyno.

Off boost response and power is remarkable and the car just leaps forward with this build but from day one it has always had more lag than anticipated. In fact it has more lag than my stock engine and stock cams and here in lays the mystery. At 10:1 compression you would think I would have to run very little ignition timing but I was really able to run much more than I should have been able to. I was also able to run 20 psi on pump gas without issue along with ample ignition timing which left me scratching my head. On the track the car just leaps out of turns with great power and awesome throttle response but jam the gas at low rpm and it struggles to boost to 20 psi before 5k rpm.

The first thing I was able to find wrong was the AVCS. Having the AVCS on or off made absolutely no difference in power or spoolup time. I was able to get the solenoids to cycle so this verified the Hydra’s outputs to the AVCS solenoids were functioning but maybe it wasn’t seeing the cams correctly so I switch the system to open loop instead of closed loop. This also netted no difference so for whatever reason the intake cams aren’t moving but the solenoids are working. This would explain part of the lag but really only about 250-300 rpms worth of blame.

Never being one to settle I had the engine pulled and inspected. We checked the compression, cam timing, boost controller, wastegate, and even did a leak down resulting in only a 4% leakage past the rings. Oil pressure was holding between 70-80 psi all the way to 8200 rpm. Of course everything checks out, no head gasket leak, valves all sealing but honestly we knew this was going to be the case given the compression and leak down tests. From day one my vacuum at idle was ridiculously low and I had my suspicions about the cams but until we tested compression and leak down I didn’t want to point the finger. The car is really acting like there is way too much overlap on the cams and I’m literally blowing the charge out the exhaust valves. From what I stated above this all really points towards this as the problem. I’ve had great luck with these cams on customer’s cars so I hope there is a problem with these particular camshafts. We’ll send them off to Cosworth so they can put them on a Cam Doctor to see if they are within spec. I have my suspicions on what may have gone wrong but I’ll wait to hear back.

At this point I am going back to the OEM STI camshafts as a control to see how the engine performs. I suspect it’s going to absolutely ridiculous with huge torque and nasty stump pulling power. LOL! I never really wanted much more than 550 whp I just wanted better throttle response, faster spoolup, and to be able to run less boost pressure.

Still 507 whp at 24 psi on a conservative tune isn’t too shabby. Here's a video of this setup in action http://elementtuning.com/Videos/SummitPoint119Web.wmv

You can read the full post about this run here: http://forums.nasioc.com/forums/show....php?t=1335874

Thanks,
Phil
http://www.elementtuning.com
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Last edited by Element Tuning; 09-05-2007 at 05:55 PM.
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Old 09-05-2007, 04:05 PM   #2
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Is the GT65 larger than a 35r?

Doug
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Old 09-05-2007, 04:07 PM   #3
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Sounds like the cam degree is off.
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Old 09-05-2007, 04:11 PM   #4
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sounds like a great dyno car. Full boost by 6000 rpm yesssssssss
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Old 09-05-2007, 04:11 PM   #5
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I run those same cams, with our long block 8.5 to 1 comp and a 35r and see 23psi @ 4500rpms on the dyno and about 4000rpms on the street. Don't think its the cams.
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Old 09-05-2007, 04:14 PM   #6
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Quote:
Originally Posted by TopSpeed View Post
Is the GT65 larger than a 35r?

Doug
from what i remember reading about it, i think they are about equivalent, with the GT65 not using a ballbearing cartridge like the Garrett turbo
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Old 09-05-2007, 04:17 PM   #7
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Quote:
Originally Posted by TopSpeed View Post
I run those same cams, with our long block 8.5 to 1 comp and a 35r and see 23psi @ 4500rpms on the dyno and about 4000rpms on the street. Don't think its the cams.
what do you think the problem might be?
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Old 09-05-2007, 04:55 PM   #8
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Quote:
Originally Posted by TopSpeed View Post
Is the GT65 larger than a 35r?

Doug
Smaller on the exhaust side, same as compressor (65 lbs/min)

Thanks,
Phil
www.elementtuning.com
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Old 09-05-2007, 04:57 PM   #9
Element Tuning
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Quote:
Originally Posted by TopSpeed View Post
I run those same cams, with our long block 8.5 to 1 comp and a 35r and see 23psi @ 4500rpms on the dyno and about 4000rpms on the street. Don't think its the cams.
Generally speaking I would not say the Cosworth cams are bad but there is no guarantee my cams were ground correctly. I would bet money they are incorrect and not ground as they should be.

I have tuned them on other cars and they perform well, that's why I put them in my engine
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Old 09-05-2007, 05:00 PM   #10
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Quote:
Originally Posted by TAPOUT View Post
Sounds like the cam degree is off.
The centerlines could be off resulting in way too much overlap which would explain my low idle vacuum.

Thanks,
Phil
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Old 09-05-2007, 05:09 PM   #11
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you have a torque graph.
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Old 09-05-2007, 05:10 PM   #12
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Originally Posted by 1sImage View Post
sounds like a great dyno car. Full boost by 6000 rpm yesssssssss
I've seen this in a few posts. Peak power is not where peak boost is but yes it's laggy but really it's not as bad as it looks. This car is making more power than a stock STI at only 4700 rpm.

On a stock engine we were seeing 20 psi by 4000-4100 rpm with the GT65 kit and there in lays the disappointment. If these cams come back normal then I will stick with the stock cams and give up the 30 hp on the top end to pick up 80 whp at 5500 rpm. This wouldn't be the first time I've seen an incorrect cam but it would be the first time it's happened to me

Thanks,
Phil
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Old 09-05-2007, 05:11 PM   #13
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Originally Posted by M.S.P.T View Post
you have a torque graph.
No because the dyno was having problems picking up my ignition so we had to run it with speed only. In speed mode it does not report torque.
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Old 09-05-2007, 05:17 PM   #14
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Interesting, I know Scott Siegel has seen similar problems on two cars recently with full Cosworth setups. I'm sure he would be happy to share what he has seen if you give him a call Phil. We also need a Hydra for the Shop Racecar.

Matt
Batlground Racing Time Attack Driver.
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Old 09-05-2007, 05:41 PM   #15
Element Tuning
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Quote:
Originally Posted by S L O W W R X View Post
Interesting, I know Scott Siegel has seen similar problems on two cars recently with full Cosworth setups. I'm sure he would be happy to share what he has seen if you give him a call Phil. We also need a Hydra for the Shop Racecar.

Matt
Batlground Racing Time Attack Driver.
Thanks I'll give him a call. Added a video to the main post.

Phil
www.elementtuning.com
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Old 09-05-2007, 05:45 PM   #16
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Sometimes it's a good idea to check your opening and closing numbers on more than one valve. What were your lobe centers and how much over lap did you have? Even running the valve clearance on the loose side of spec can help bring the idle vacuum up. If you have enough piston to valve clearance lower lobe centers would help too.

Oh Yeah, one other thing. Did you actually measure the compression ratio? I've had pistons that were supposed to be 13.5:1 actually end up being 14.5:1. Sometimes the piston makes don't have all the gasket thicknesses and head volumes right when they quote compression ratios.

Last edited by gumby647; 09-05-2007 at 06:01 PM.
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Old 09-05-2007, 06:10 PM   #17
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Quote:
Originally Posted by gumby647 View Post
Sometimes it's a good idea to check your opening and closing numbers on more than one valve. What were your lobe centers and how much over lap did you have? Even running the valve clearance on the loose side of spec can help bring the idle vacuum up. If you have enough piston to valve clearance lower lobe centers would help too.
The advertised cam specs are very good:

Intake @ .010"
Degrees: 278
Cam Lift: 10.9 mm
Centerline: 107
Open: 29.5 degrees BTDC
Close: 69.33 degrees ABDC

Exhaust @ .010"
Degrees: 274
Cam Lift: 10.3 mm
Centerline: 113
Open: 70.9 degrees BBDC
Close: 23.4 degrees ATDC

We will send them back to get verification of these numbers.

We have lots of piston to valve clearance with our custom pistons and won't be limited here. Idle vacuum is only 12-13 inHg at best. We double checked the valve clearance and it's exactly at what's specified for these cams. No there is no vacuum leak

Now we built two motors back to back, one for a customer and one for our Time Attack car. The customer's motor with these cams has normal vacuum at around 18-19 inHg and normal spoolup from my experience with these camshafts. I had to wait for my camshafts as they came in on a different shipment than the other set. We verified the camshafts and all the specifications of our build as we keep meticulous records and pictures that show the part numbers of the camshafts in the head. I will be shocked if these cams come back measured to advertised specification given my normal experience with them.

Thanks,
Phil
www.elementtuning.com
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Old 09-05-2007, 06:33 PM   #18
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So you didn't check them with a degree wheel? I'm used to looking at cam numbers @.040" or 1mm lift so those look weird to me. Also the 113 LC on the exhaust is kinda big I'd try running it down to 107 and see what happens, I've run as low as 99 on some engines to get a good curve you just have to keep running it on the pump till you find what works best.

I'll add here that all my engine tuning experience is with NA engines albeit NA engines making over 200whp per liter. Although I'm pretty sure the tunning principles are the same.
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Old 09-05-2007, 06:37 PM   #19
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Very interesting. I have the same cams (p/n KK3766 right?). I have lower vacuum at idle than others I have talked to (-400 to -430mm/hg on my avcr) and I see 22-23psi by like 4700. Not sure if AVCS is working or not... the ecu thinks it's working.
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Old 09-05-2007, 07:02 PM   #20
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Small intake leaks.

I know because I still have them and all the symptoms you describe. I had my car once with perfect seals on the intake (still don't know why I messed with it). I could pressurize the intake system in about 4s with an air compressor...and it would hold for a good 15-20s before going down below 15psi. The car was so snappy then, but now I have small leaks and can't find them.


I really, really doubt Cosworth messed up the cam machining.

Bill
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Old 09-05-2007, 07:23 PM   #21
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I have the same cams in my built motor and usually see about 16inHg of vacuum at idle on my Zeitronix gauge as compared to about 19inHG of vacuum when I had the stock cams in the stock motor. That kind of moderate drop in vacuum seems about right me. 12-13inHG would certainly seem to indicate a problem with the cams or some fairly sizable vacuum leaks.
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Old 09-06-2007, 12:08 AM   #22
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Leaks would only show up as poor vacuum and not result in such an increase in spoolup time. I know of at least a couple of bad sets of cams from Cosworth and more from others (By the way Cosworth cams are outsourced and not made in house just ground to their specification). It happens no matter what company as there is still a human that has to set up the machine and put the correct billet in I'm not trying to be a Cosworth hater, I did buy these cams after all based on positive experiences.

Last edited by Element Tuning; 09-06-2007 at 12:16 AM.
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Old 09-06-2007, 02:20 AM   #23
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Maybe its car karma? You know, for c*ck-teasing a car due for a tune to go race in Portland. But what do I know, right?
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Old 09-06-2007, 04:08 AM   #24
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Quote:
Originally Posted by Element Tuning View Post
Leaks would only show up as poor vacuum and not result in such an increase in spoolup time. I know of at least a couple of bad sets of cams from Cosworth and more from others (By the way Cosworth cams are outsourced and not made in house just ground to their specification). It happens no matter what company as there is still a human that has to set up the machine and put the correct billet in I'm not trying to be a Cosworth hater, I did buy these cams after all based on positive experiences.
Blowing fresh charge out the exhaust, but no backfiring? Isn't this a catless car?

If the cams end up being in good spec, it could just be that the much smaller combustion chamber is more quickly scavenged.

Air leaks could be ruled out by connecting a MAF sensor and figuring out if there's any air getting in which can't be accounted for.

Sounds to me almost like the IVC is just a lot later than ideal for that setup. Total cylinder volume changes more dramatically in high compression engines as the piston rises. So a very late closing angle on the intake valve can leave very little gas in the cylinder to combust, and thus very low VE, making idle vacuum very low too.

Anyway ... just tossing some ideas out there ...
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Old 09-06-2007, 10:54 AM   #25
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Originally Posted by SaabTuner View Post
Blowing fresh charge out the exhaust, but no backfiring? Isn't this a catless car?

If the cams end up being in good spec, it could just be that the much smaller combustion chamber is more quickly scavenged.

Air leaks could be ruled out by connecting a MAF sensor and figuring out if there's any air getting in which can't be accounted for.

Sounds to me almost like the IVC is just a lot later than ideal for that setup. Total cylinder volume changes more dramatically in high compression engines as the piston rises. So a very late closing angle on the intake valve can leave very little gas in the cylinder to combust, and thus very low VE, making idle vacuum very low too.

Anyway ... just tossing some ideas out there ...
Trust me no air leaks as this was the very first thing we tested but also I knew a vacuum leak would not result in the robust ignition timing I'm able to run with such high compression or the poor spoolup. It's very possible these cams are mismatched to this compression but I'm not convinced of this given the advertised cam specs. A low VE overall could result in the late spoolup and the ample timing I can run or just the extra cylinder pressure from the high compression pistons is escaping due to the overlap.

Also I tried to advance the intake cam from 0-15 degrees over a wide rpm range trying to improve the spoolup. The problem with this is that while it will close the intake valve earlier reducing overlap when the exhaust valve opens it also opens earlier which increases overlap when the exhaust valve is closing. It's almost as if the engine wants me to retard the intake cam. These situations really make me want to get an engine dyno

I will put the stock cams back in as a control, test, and then move on from there. If Cosworth checks the cams to be at spec well then I'll have to have custom (like everything else it seems) cams ground for me. This is why we test. Sometimes it works the first time and sometimes it takes a few tries.

Thanks,
Phil
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