VINCE

iTrader: (1)

I am planning on going bigger in the future.. So JMX your 2.08's made the same as your 2.02's. Did you lose any power under the curve with the bigger valves? What about throttle response..?

jmX

Vmoore, well, the comparison isnt exactly fair since the 2 sets of heads were ported by different places, but here's the graph of my IRS Stage 2 2.02/1.575 heads overlaid on my ARE stage 2 2.08/1.60 heads.

http://home.austin.rr.com/jmx/car/irs_vs_are.jpg

The lowend difference is just because the dyno was started at a different RPM, and the topend issue is some sort of valvetrain issue I've been having (it is not infact the guy letting off the gas, like the jpg says).

Throttle response was the same, if not better with the ARE heads.

Again, who knows if the ARE heads woulda made a bit more with smaller valves...I'll never know, but I'm not really concerned.

Visceral

iTrader: (1)

mmmkay,

"Stage 3" or so its called, is where the intake valve is scooted over towards the middle of the bore as much as is possible without bumping into the exhaust valve. Theres about .030 there that you can scoot. THerefor I would be getting the same shrouding (same distance from the cyl wall) as the 2.02 valves without the scoot.

It could be shrouding, but I didnt think shrouding "materialized" from 5.5k up.

Im thinking tuning or exhaust backpressure.
I have the SpinTech "Loud as Hell" 4" muffler, which MTI does not like much. They say I will pick up power moving to something else, even a 3". For the purpose of the Open Track Challenge next year, I'll probably just run a XR-1 in the Spintech's place. THen on with a Corsa.

thanks for all the replies so far. I'll keep you updated as I hear from MTI.

chris

Visceral

iTrader: (1)

[quote]Originally posted by 1madss:
<strong>Wow, your dyno looks almost just like mine. I have the MTI S2 heads and hammer cam and peaked at 408.7hp and 388.3 tq right about 6000. My car is going rich ~6K. That and my timing is not so great after 4K. What do your A/F and timing numbers look like. Also, any idea what that burble in the hp and tq lines are at 5-5.5K?

Mark

[ November 26, 2001: Message edited by: 1madss ]</strong><hr></blockquote>

Did MTI have any suggestions as to how to fix the richness over 6k? MTI is doing my dyno'ing, and I havent even seen the car since its been running, so I dont have any idea what the timing and A/Fs look like. I sure would be interested though. Then I would have to use a MAFT (whatever thats worth) until LS1 Edit comes out.
Lesee... LS1 Edit and Electric water pump. Can I ever stop paying out $ on this car???? <img src="images/icons/grin.gif" border="0">

chris

1madss

iTrader: (10)

I'm pulling the PCM and sending it out to MTI sometime this week for programming. I don't think MAFT would do me any good as I am pretty lean up until 6K. I would talk to Jayson and see what he has to say about your Timing and A/F. That's where I would look before worrying about shrouding. But then again, I'm hardly and expert <img src="images/icons/grin.gif" border="0">

Mark

VINCE

iTrader: (1)

Thanks jmx for the comparison dyno graphs. That really helps me alot.. I looked at my peak horsepower on my last dyno and at points you were 20 to 30rwhp higher than my setup with stock heads. Then you peaked just about 15rwhp higher than me.. Your cam seemed to peak right between 6k and 6200rpm and mine peaked at 6400rpm.. Now I see where people say the power under the curve is what counts more.. Now I do not think it is shrouding since both valve setups produced identical power..

VINCE

iTrader: (1)

Same thing when I looked at Vis dyno.. He is about the same as mine then around 4k his power starts inching up by 10rwhp and by 5500rhp he is 30rwhp higher than my stock headed car and then peaks about 20rwhp higher than I ..

Terry Burger

iTrader: (4)

Larger than 2.02 valves add $400-$600 to the price of heads I believe. Doesn't seem like its worth it to me, unless you are running a 4" or larger bore.

jmX

[quote]Originally posted by Terry Burger:
<strong>Larger than 2.02 valves add $400-$600 to the price of heads I believe. Doesn't seem like its worth it to me, unless you are running a 4" or larger bore.</strong><hr></blockquote>

Didnt add any cost to my heads over normal valves...I got my price quote and THEN was asked what valves I wanted to go with.

Like I said, it allows me to do a big bore later and not have the heads retouched...somebody can just ship me a shortblock and I'm set to go.

Visceral

iTrader: (1)

[quote]Originally posted by Terry Burger:
<strong>Larger than 2.02 valves add $400-$600 to the price of heads I believe. Doesn't seem like its worth it to me, unless you are running a 4" or larger bore.</strong><hr></blockquote>

Didnt cost me a dime.

"Never had one lesson!" :-)

chris

Ragtop 99

iTrader: (7)

Back to his original question... <img src="images/icons/wink.gif" border="0">

Have you looked at your injector pulsewidths in ATAP. You may be running out of fuel.

Do you have cats?

Visceral

iTrader: (1)

[quote]Originally posted by Ragtop 99:
<strong>Back to his original question... <img src="images/icons/wink.gif" border="0">

Have you looked at your injector pulsewidths in ATAP. You may be running out of fuel.

Do you have cats?</strong><hr></blockquote>

I have one orange Devon Rex and a tabby fat bitch. <img src="images/icons/wink.gif" border="0">

But I have no catalytics.

MTI claims Im not particularly close to the fuel limits. They dont know this because they looked at my car though... They just believe that based on previous work. I would think that it would at least have stayed flat though if I ran out of fuel, rather than falling off. I think its airflow related, for some strange reason.

chris