Dynamic compression ratios DCR

[sanguissaevus]

sanguissaevus - Sorry, my cam was a 225/234, same lift as in my other post. My int valve closed at 44.5 degrees @.050 with the cam installed straight up. I ******** it 2, 3 and then 4 degrees. Ended up with sticking with 46.5 degrees. I couldnt tell any change. My cranking pressure held at 195psi on a hot engine.
Never ran into any engine ping with 93oct gas. I will give credit to the JM heads, tight quench and the Dan Cragin tune for that.

If I punched all the numbers in right your DCR is something like 9.16. I was using the calculator off of http://members.uia.net/pkelley2/DynamicCR.html at the bottom of the page. Very interesting. Your dyno sheets are very impressive. Any time slips? I'd love to see your trap speeds. You said this was your "old" Viper. Did you sell it? What do you have now?

 

[Camfab]

My numbers are very similar to vp97. As an FYI, I am very familiar with runner length theory. 600 RWHP and lb/tq is very much attainable with the stock intake manifold in its unported state.. Yes it's going to have a very nice lope at idle, and off idle its going to make more power than stock. Actually having a nasty idle was #1 on my list of must haves. Take the experts word how ever you'd like, Jeff flat out told me that the gen III manifold will give up tq everywhere AND not make it up on top, he was adamant that the Gen II manifold will make power. I even inquired about having a custom sheet metal intake constructed. Again the same answer. Unless you've got an all out full race application, your going to lose power. You don't need to spin these engines past 6k anyway, it's not a small block Chevy. Spin it hard and you'll get a nice surprise. I also think "Big Cam" is a relative description as well, my old car had a 260/270 @ .050 on a small block Chevy, it was my daily driver. It had 1" of vacuum at idle, that's a pretty big cam, that could and did use a short runner manifold. Maybe if you spun the Viper engine to 7k and were running 12.5:1 could I see the need for a big cam and a short runner intake. Otherwise I think 600 at the wheels and not giving up any midrange would be the best combo for a basic street viper. I've been to the track a few times, and I've been booted off every time before I can get a real pass in. She runs 129 without break'n a sweat in the qtr.

As far as it being blown, I agree, there's nothing like a forced induction engine. I thought that one out long and hard, but I decided against it for two reasons. The first being the extra 120 lbs of weight over the front wheels. My second thought was, it's all in the cylinder heads. If you build the foundation properly, you can always upgrade to a blower down the road, with spectacular results.

 

[1BADGTS]

Right if you are going to keep the gen 1/2 intake then the rest of the parts have got to peak in the same RPM band and focus on lifting the entire opperational RPM band which does not extend beyond about 5700 RPM or so. These intakes are good for ABOUT 550 RWT and 500 RWPH without much trouble. After that you are fighting the intake, spending stupid money and sacrificing idle characteristics for tiny gains.

I spent thousands on the stock manifold to get it to flow better (It was extrude honed,cut apart and hand ported to the tune of 20 hours labor and then extrude honed again .The flinal flow numbers were sent to Crower Motorsport where in conjunction with my head flow numbers a cam was made.Net result over 10k on cam heads intake work and the car was no faster

 

[1BADGTS]

If you guys look at the history of these cars the fastest TRUE STREET Gen 2 Vipers were the Lingenfilter 550 Cu Strokers that on stock tires trapped around 134 and my old Gts on 490 cu that trapped near 132 .By true street= full interior ,pump gas ,exhaust system and a hyd cam.LOL one year at the Viper Nat Drag events some guy with a 750 TNT KINGSNAKE showed up and produced a dyno sheet that read 650 to the tire .He then proceded to run 126 mph in the quarter .If that car was making what he dyno CLAIMED it was making he would have been and easy 137 plus

 

[sanguissaevus]

My numbers are very similar to vp97. As an FYI, I am very familiar with runner length theory. 600 RWHP and lb/tq is very much attainable with the stock intake manifold in its unported state.. Yes it's going to have a very nice lope at idle, and off idle its going to make more power than stock. Actually having a nasty idle was #1 on my list of must haves. Take the experts word how ever you'd like, Jeff flat out told me that the gen III manifold will give up tq everywhere AND not make it up on top, he was adamant that the Gen II manifold will make power. I even inquired about having a custom sheet metal intake constructed. Again the same answer. Unless you've got an all out full race application, your going to lose power. You don't need to spin these engines past 6k anyway, it's not a small block Chevy. Spin it hard and you'll get a nice surprise. I also think "Big Cam" is a relative description as well, my old car had a 260/270 @ .050 on a small block Chevy, it was my daily driver. It had 1" of vacuum at idle, that's a pretty big cam, that could and did use a short runner manifold. Maybe if you spun the Viper engine to 7k and were running 12.5:1 could I see the need for a big cam and a short runner intake. Otherwise I think 600 at the wheels and not giving up any midrange would be the best combo for a basic street viper. I've been to the track a few times, and I've been booted off every time before I can get a real pass in. She runs 129 without break'n a sweat in the qtr.

As far as it being blown, I agree, there's nothing like a forced induction engine. I thought that one out long and hard, but I decided against it for two reasons. The first being the extra 120 lbs of weight over the front wheels. My second thought was, it's all in the cylinder heads. If you build the foundation properly, you can always upgrade to a blower down the road, with spectacular results.

Yes, I didn't expect to run into any real issues with just heads/cam in regards to intake manifold flow. Like you said it's good to 600's at least. My next planned stage however I expect it to be an issue as I am shooting for an all out NA build utilizing water/****, high compression and built bottom end (not sure if I want to go stroked or de-stroked to an over square for high rpm). Whichever route I take will dictate ITB's or a sheet metal job. I was thinking maybe extrude honing the stock one after I looked inside mine when I took it off. It's very rough and could definitely benefit from smoothing. Maybe throttle bodies too. I don't know. Because I probably won't stay with the stock intake due to future mods makes me hesitant to spend money on it for gains in the interim. We will see. I am much more focused on the headers because I'm still running the stockers and I know there is much to be gained from them.
As far as sound, I too want that evil sound from the cam. Nothing sounds better to me than a nasty all motor build. There isn't a blow-off valve in the world that can beat it.

 

[sanguissaevus]

If you haven't already, check out 345sbespinnin youtube vids with his greg good heads/cam 3rd gen. He is posting 165's in his half mile events and just a few ticks off 200 at the Texas mile (he has a vid showing speedometer going over 200 at the event but I remember reading something he posted saying it wasn't accurate for reasons I can't remember). He is trapping 133 in the 1/4 too. One of his texas mile event vids has a good sample of his idle...very nice. HP numbers in the mid 600's. Best vid is his 1/2 mile event where he walks a bolt on GTR and GT500.

Just so this post is somewhat on topic...Anyone have those stock cam numbers I'm looking for (lobe separation and intake centerline for 2000-2002)? There was a Viper registry section that had this info but I can't access it. I think it was removed.

 

[1BADGTS]

Yes, I didn't expect to run into any real issues with just heads/cam in regards to intake manifold flow. Like you said it's good to 600's at least. My next planned stage however I expect it to be an issue as I am shooting for an all out NA build utilizing water/****, high compression and built bottom end (not sure if I want to go stroked or de-stroked to an over square for high rpm). Whichever route I take will dictate ITB's or a sheet metal job. I was thinking maybe extrude honing the stock one after I looked inside mine when I took it off. It's very rough and could definitely benefit from smoothing. Maybe throttle bodies too. I don't know. Because I probably won't stay with the stock intake due to future mods makes me hesitant to spend money on it for gains in the interim. We will see. I am much more focused on the headers because I'm still running the stockers and I know there is much to be gained from them.
As far as sound, I too want that evil sound from the cam. Notctehing sounds better to me than a nasty all motor build. There isn't a blow-off valve in the world that can beat it.

There are a FEW things you should realize berore you invest in approx 70k in trying to build the above.The stock oiling system will never support what you are trying to build .You will need to duplicate baisically a street version of the Cald Dev GTSR.No one has done it because its no cost effective

 

[1BADGTS]

There are a FEW things you should realize berore you invest in approx 70k in trying to build the above.The stock oiling system will never support what you are trying to build .You will need to duplicate baisically a street version of the Cald Dev GTSR.No one chas done it because its no cost effective

If memory serves me correct the 3 and 5 main bearing journ were prone to failure in high rpm apps .The dry sump oiling system on the GTSR would have to be incorporated and i dont think it works with the stock block (need the GTSR BLOCK )You also will need a fuel system as stock is inadequate .Hogan used to make a sheet metal intake for around 4 to be used solid cam Even if you could find a GTSR BLOCK and dry sump system at a reasionable price many of the stock brackets will not fit The entire idea is an easy 70k project whose street manors would be terrible

 

[sanguissaevus]

If memory serves me correct the 3 and 5 main bearing journ were prone to failure in high rpm apps .The dry sump oiling system on the GTSR would have to be incorporated and i dont think it works with the stock block (need the GTSR BLOCK )You also will need a fuel system as stock is inadequate .Hogan used to make a sheet metal intake for around 4 to be used solid cam Even if you could find a GTSR BLOCK and dry sump system at a reasionable price many of the stock brackets will not fit The entire idea is an easy 70k project whose street manors would be terrible

Yes, i anticipate burning rediculous amounts of money building my dream car. Im sure there are many other pricey details to hash out. Time is money and I dont plan selling this car anytime soon. Hee-hee, manors....not in my vocabulary.

 

[Dan Cragin]

One neat option is a short stroke engine, its been done and I drove a street car like this that was just amazing. With a much broader 7500rpm powerband you have a lot of area to work with.
With a good short block, solid cam, light valvetrain and a budget external (wet) oil pump system, this can live.

 

[ericj96]

If I punched all the numbers in right your DCR is something like 9.16. I was using the calculator off of http://members.uia.net/pkelley2/DynamicCR.html at the bottom of the page. Very interesting. Your dyno sheets are very impressive. Any time slips? I'd love to see your trap speeds. You said this was your "old" Viper. Did you sell it? What do you have now?

I assume you are aware that DCR is not based on duration at .050 intake closure. Its based on .006 or .000. Makes a big difference.

 

[sanguissaevus]

One neat option is a short stroke engine, its been done and I drove a street car like this that was just amazing. With a much broader 7500rpm powerband you have a lot of area to work with.
With a good short block, solid cam, light valvetrain and a budget external (wet) oil pump system, this can live.

Yes, this is what I was referring to as "over square" engine by de stroking it. I didn't know there were any Vipers that did this yet. I've read about some corvettes doing it with great results though. Very cool. Good info. If you have more details on this guys setup I would love to hear it.

 

[sanguissaevus]

I assume you are aware that DCR is not based on duration at .050 intake closure. Its based on .006 or .000. Makes a big difference.

Yes, I'm aware. That one article pointed this out too. I glazed over it though. Saw the 46.5 degrees and didn't see the uncorrected 44.5 @.050. Oops. Should be roughly a 50 degree disparity between .050 and .000. VP97, do have this info?

 

[1BADGTS]

Yes, i anticipate burning rediculous amounts of money building my dream car. Im sure there are many other pricey details to hash out. Time is money and I dont plan selling this car anytime soon. Hee-hee, manors....not in my vocabulary.

Best of luck. You can trust Dan Craigen more so than just about any tuner on here to give you good ,sound practical advice.

 

[1BADGTS]

One neat option is a short stroke engine, its been done and I drove a street car like this that was just amazing. With a much broader 7500rpm powerband you have a lot of area to work with.
With a good short block, solid cam, light valvetrain and a budget external (wet) oil pump system, this can live.

Danny, Nick has done a bunch of the short strokers but never with the solid cam .Dave (Crower )told me years ago that with the right combo they were REAL STRONG but i just had enough with the tinkering if you know what i mean.LOL The last time the magazine guys bent the crank instead of a short stroke i wanted to go full stroke untill i saw the price of the 550cu crankshaft from Cleveland Crank (8k )Buy the time i was done to pick up a few horsepower (the 550cu LPE cars were running a hair faster than me )it was not worth it (crank new rods and pistons ect )Dan if you ever need pistons Manley (NJ )will make them for the Vipers now .The quality is almost JE (equal to the Ross )and priced better than either .