[Acuranerd]

See, this is what I love. I know a "certain" hatchback that has a 21.53:1 Dynamic CR........oN PUMP GAS!!!

The problem is that there are other factors that contribute to the dynamic compression ratio of an engine under boost, that arent accounted for in this calculator. i.e. head flow, turbo flow, and cam overlap.

Even so, it's fun to play with.

 

[Acuranerd]

Also, for those of you that have see the infamous 'Civic beats Viper' video that is floating around the internet, that car had a Dynamic CR of 24.81:1, on 93 Octane. Stock VTEC cams were used, so for about 40 degrees of camshaft rotation, boost was being shot straight out to the exhaust.

 

[Acuranerd]

Why wouldn't cam overlap affect the dynamic CR? Where do you measure boost? The CR Calculator is based on manifold pressure, not actual boost used. There are too many variables for a simple calculator to determine the Dynamic CR.

 

[Acuranerd]

Here is my reasoning. In short, the reason why overlap affects the DCR is because while you are on the compression stroke, the exhaust valve is still open, therefore you are losing some of your compression out of the exhaust. That is why FI cars use short overlap cams.

 

[Acuranerd]

DCR is your way to put limit's on boost pressure. It really doesn't matter. That calculator is based on the Static CR and manifold pressure. Just stick to your N/A Applications and I'll stick to turbochargers. I think we'll get along better.

It's easy to use math to calculat things, but until you actually try it, the numbers mean nothing. That's why we can run 20 lbs. of boost on a stock LS motor and not blow anything up.

 

[Acuranerd]

The engine's boost limit's are much greater than most people think they are. You would be supprised how much absuse these little Honda engines can withstand. And yes, I am fixed on boost, I'm a boost junkie.

I just wanted to make the point that the DCR isn't something to worry about, nor is it something I've ever tried to control. It's like the rod ratio. The LS doesn't have a good rod ratio, but I have no problem revving my LS to 8k, stock head/ecu and all.

Anyhoo, if your ever in Houston, Texas, let me know and I'll bring you to the shop and show you some of the stuff we do. We just built what will be the fastest Viper in the world. on the previous setup it ran [email protected] With the new setup it has a fully built motor, and a 2 stage nitrous setup which should propell the car into the 9.4 range.

on Sunday we did a test and tune session at Houston Raceway park where we tested a 768hp h22 powered Prelude. That's right 768fwhp, and 734tq on a street driven prelude. Fully built, of course. If you live on the SE side of houston and see a stock looking Red Prelude with 't00ned' stickers on the side, don't race him unless you want to loose, badly.

We've supprised many a heads/cam nitrous LS1 and heads/cam blower 5.0's.

 

[Acuranerd]

It's kind of a shop secret. If you found a way to do something nobody else knew how to do, I don't think you would run around telling everybody. As for reliability numbers, the car has been running 20 lbs. of boost, everyday, for the last 8 months, and not a single problem. The Hondata also hasn't been readjusted with the changing of the weather, and here in Houston, the weather goes from about 50 in the Winter, to almost 100 in the Summer, so I think were doing pretty well.

I would like to help everybody out by telling you guys what exactly has been done to the engines, but I've agreed not to. I'm just trying to get people to think on their own and not to listen to what most people will tell you, especially the magazines.

I know virtually nothing about setting up a car for a NA motor. So I couldn't tell you anything about the Toda cams, other than I wouldn't run them in a boosted motor.

Oh, BTW, the hatch I've told you about will be in an upcomming issue of SCC, you should check it out. I don't know if you get that up their, though.

I can post the dyno for the hatch if you like, but I don't have any webspace to host it, so I would need somebody to host it for me.