Would anyone know the volumetric efficiency of a stock 4g63?
I’m trying to figure out CFM using:

cid x rpm x .5 x v.e. (Volumetric efficiency)
------------------------
1728
= Basic cfm

14.7 + psig
---------------- = Pressure ratio.
14.7

Basic airflow x Pressure ratio = Airflow under boost.

Is this the most accurate way of calculating?

 

big bump for some very interesting reading.

 

I like the percentages better than raw numbers... much more usable from across the country... not to mention it cuts out the major bull**** postings.

I wish the whole dyno thing would have been done the same way... still not apples to apples, but easier to digest.

 

Can we have a comparison (in % difference, not CFM) to a stock 1G and stock 2G DSM head? After seeing that you can't maintain high boost on the BR 475 on the EVO but you CAN maintain high boost on the BR 475 on the DSM's I was wondering if it is due to limitations in the head flow.

Thanks,

Keith

 

Not sure what kind of 16g you have but I have never seen or heard of one holding 25 psi to redline, it's not going to happen.

The stock EVO head actually flows about the same as the 1g head after going back and comparing the charts side by side. I was just surprised to see it completely stall at .300 lift.

The stock turbo can spike to high boost, we have seen 28+ psi on the spike. It quickly drops off to 21 psi or so.

The head we have been running to 8,000 rpm with the stock parts in it. The spings may be an issue as they are very weak. That may be part of what we are running into.

Stock rods are in our car. I just heard about 2 other shops throwing them out of the pan last week though. We have made 429 whp so far on them and run them to 8k rpm.

The 264's will not make power past 8,000. Neither will the turbo or head though.

David Buschur
www.buschurracing.com

 

I can't find the stock 2g head flow charts. I think I shredded them last week by mistake, crap!

Here are some comparisons to add to this stuff though.

stk 1g int lift
+10% .100
+9% .200
+4% .300
+7% .400
+6% .500

stk 1g exh lift
0% .100
-4% .200
-4% .300
-3% .400
-1% .500

There, I actually figured it out. The numbers above will show how the stock 1G head compares to the EVO head stock. The difference is the 1g intake port is alot faster than the EVO. The exhaust port on the 1g is slightly slower BUT doesn't stop flowing, big deal I guess as it doesn't flow as much anyway.

Now, here are the 1g Stage 3 ported head numbers compared to what we have finished SO FAR on the EVO. This is where it gets crazy.

1g BR Stg 3 Intake lift
+1% .100
+5% .200
+5% .300
+6% .400
+12% .500

BR Stg 3 1g head exhaust lift
-3% .100
+9 .200
+25% .300
+15% .400
+7% .500

As you can see we have the exhaust port on the EVO head flowing like mad. I'd like to have these numbers on the 1g head in my race car!

Just more information.

David Buschur
www.buschurracing.com

 

Oh brother! I got the head back today, HOLY CRAP does this thing flow with the new valves in it. I am absolutely stunned at the results.

The only thing that I don't like is the guy that flowed the head used a pipe on the exhaust port. I don't like doing this. What it does is straightens out the airflow at the end of the port. The CFM, as far as I know, always increases. He didn't flow the exhaust without the pipe which is useless as all the other tests were done without it. I will have to have the exhaust port flowed again.

The results below are the percentage over stock.
Check this out.

Intake mild porting stk valves additional porting large valves

lift
.100 4% 27%
.200 1% 19%
.300 4% 14%
.400 9% 19%
.500 8% 20%

I will post the exhaust gains as soon as I can get the head back on the bench again.

David Buschur
www.buschurracing.com

 

I'm never going to be able to afford all of this...

 

David,

Maybe I'm an idiot but I'm a bit confused by what you have posted here. The percentages you have posted are the increase (or decrease) in flow of the Evo head when compared to the 1g head, or the 1g head when compared to the Evo head?

 

what he said HIGH HIGH can we rev???? just wanted to know as for comparison boost solutions valvetrain work will be able to rev between 9500-10000

-non

 

I guess it is a little confusing.

First two graphs show the gain or loss of the EVO head compared to a stock 1g head.

The second set of graphs show the gain or loss of the ported Stg 3 EVO head compared to the ported Stg 3 1G head.

Does that help?

As for how high you can rev. I don't know what Boost Solutions is doing for a valvetrain. We have taken the stock EVO stuff to 8,000 rpm. To be honest I think the springs are part of the problem with the car holding boost, they are just weak.

The spring/retainer kit we have for the EVO are the best numbers (overall)I have tested for a spring/retainer kit on a 4g63. The complete kit is $200. These will allow you to rev the engine to 10,000 rpm if all else is right.

David Buschur
www.buschurracing.com

 

So then comparing stock to stock the Evo head flows better on the intake side, but worse on the exhaust side based on the numbers. But then you say the 1g head is faster on the intake side, slower on the exhaust side (how does speed compare to flow?), but the 1g head continues to flow but flows less. This sounds like a contradiction to the numbers to me. Am i still not getting something?

 

very cool david...10K is very cool actually able to really use one of the big tachs now anyways... keep us up to date on the port so we can save our pennies to buy the port and valvetrain... also if we purchased at the same time would we get a decent break on the labor to install the valvetrain since everything is out of the car...

-non

alsoany projections of cost for the port

 

After reading this, you will have.

6-bolt block
1G rods
2G pistons
1G head, unported
1G intake manifold
HKS 264 cams
3" turbo-back exhaust
Evo III Big 16G

The Evo III Big 16G held over 25psi to 7339RPM, when I shifted out of 3rd gear (datalogged). It flowed a datalogged (with DSMLink) 44.1lbs/min of airflow. I ran 118mph with it in the 1/4 in my 3315lb car. With me in the car, of course.

I have attached a picture of the datalog.

Boost spiked to 29.6psi (which is as high as the GM3Bar sensor will go) after I shifted into 3rd gear. And it fell to 25.8psi. You can see the cursor is at 7339RPM, and the GM3Bar sensor is reporting 25.8psi.

The turbo is unported and unclipped. I think that porting the wastegate on these turbos actually hurts them since the flapper is more likely to blow open, which lowers boost.

My old small 16G was TRE ported, and had the 34mm flapper valve. I couldn't hold more than 19psi at redline with that sucker. The flapper door was being blown open. Force on the wastegate actuator arm goes up with the square of the radius of the valve. So the bigger the flapper is, the worse off you are.

I ran a best of 112.5mph with that turbo.

With the exact same setup, and the 3rd time out with the Evo III 16G, I ran 118mph. Of course, the Evo III big 16G is actually larger than the big 16G, and has a lighter compressor wheel. The best of all worlds, IMO. Spools fast, and flows an HUGE amount of air. I was pretty much the first guy to really push the Evo III 16G hard. I think that you will see other people posting similar numbers in the coming year.

Dave, hopefully I'll get to the shootout this year. I've been going for the past 6. I have a couple trophies on my mantle from your events. Thanks!

 

So I guess going cheaper is better!!! Amazing! I guess we will be having a lot of 25psi boosting EVOs on the street and 30psi EVOs at racetracks!!!

Later Subies!