Some facts about head flow

HAM Inc · Post by **HAM Inc** » Tue Jul 26, 2005 11:35 am

I just finished reading the latest T1 vs. T4 debate on the Samba. I know a lot of STF regulars checked in on it too, so I thought I would go ahead and post some info. that should debunk some myths and perhaps shed some light on what an experienced head tech looks for in the relationship between in and ex ports.
First I'll go ahead and post the flow #'s for a stock 1.7. These #'s were generated on my digital flow bench using Audie Tech software and hardware. The test was conducted with a 28" depression on a bone stock 1.7 complete with carbon on the valves.
lift in ex
.050" 38.2 25.8
.100 64.4 45.9
.150 80.4 63.4
.200 98.5 77.9
.250 112.9 86.9
.300 123.6 90.9
.350 134.1 92.6
.400 143.7 94.0
.450 151.2 95.0
.500 156.4 95.8

Now these #'s are FAR superior to a stock 1600 DP. Also if you calculate the In/Ex. ratio you'll find that the average ratio is in the 75% range. This is more in line with modern approaches.

The Type 1 design (and the 356/912) design represents the prevailing belief during the first 50 years of engine development that an ex. port needed to move a very high % of the intake as a means of reducing negative torque, (less resistance to the rising piston). This theory gave way as H.P. cam grinders and racers determined that, while the higher ex. flow % lead to an increase in net torque, the improvements in acceleration and drivalbility that resulted from lowering the ex. % more than made up for the small reduction in net torque. By the early sixties the 75% value became a benchmark that remains for normally aspirated engines. Ofcourse there are worse things than having an ex. port that outperforms this %, but race head porters take this very seriously.

I like to see a very high % for the first .200" lift on high speed engines as this is generally around the lift that the ex. valve has when the piston hits BDC. Meaning that the flow is high during the critical blow-down period. I don't consider an ex port to be restrictive unless these early #'s are below 85% and if the average % is below 70%.

It is much easier for the cam grinder to compensate for an underperforming ex. than an underperforming intake.

The t4 ex port has a nasty reputation because (I guess) it looks restrictive. The first time I held a t4 head in my hands I felt the same way. The truth is the port ratios on all t4 heads are right around 75% in stock form. (With the 1.7 having the lowest flow values and the 2.0 914 having the highest)

Another interesting truth about these heads is that over time I have found that, on average, 15 minutes of ex port work will require around an hour of intake port work to keep the ports balanced. This underscores the importance of knowing what you are starting with before you start carving up ports on any head.
I have also found that it is VERY easy to modify a T4 ex. port such that the ratio shoots into the 80% range. I have flowed heads prepped by well known T4 head specialists that flowed in 85% range! I point that out not as a knock against anyone, just as way to highlight the fact that the mythical T4 ex. port limitations are just that, a myth

Kenny2428 · Post by **Kenny2428** » Tue Jul 26, 2005 11:39 am

I wonder if danimal will read this?? Lol, awsome.

type11969 · Post by **type11969** » Tue Jul 26, 2005 11:57 am

What is the link to this discussion on the samba? I gotta read this. I wonder how many varmits met their maker while Jake was reading it . . .

eric wagner · Post by **eric wagner** » Tue Jul 26, 2005 12:29 pm

type11969,

http://www.thesamba.com/vw/forum/viewtopic.php?t=125306

I thought it was a pretty interesting topic.

Eric

vw505 · Post by **vw505** » Tue Jul 26, 2005 12:35 pm

Hey Len, so how are my heads coming ? take your time i am in no rush.
mike

tuna · Post by **tuna** » Tue Jul 26, 2005 12:49 pm

Thanks Len for sharing that. Danimal's ranting were getting very annoying, and his assumption that I was "hiding" T4 head flow #s was very aggravating. I'm not a cylinder head specialist, just a enthusiast who shares what he learns, for the greater good of the community.

How long does it take to flow a cylinder head? How much do you charge to do it? Just curious....

Keep up the good work, and I know I made the right decision for you to do my heads. I can't wait to see them!!

Tuna

Plastermaster · Post by **Plastermaster** » Tue Jul 26, 2005 1:13 pm

Good info Len, but I prefer to get my head information form people like Dan who have never had a T4. That way the info is more objective. How many T4s have you videod anyway?

OOOHHH I couldn't help it.

Ron

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Tue Jul 26, 2005 3:07 pm

Yeah- We'll see if he ever notices it here.... I know he checks the forum, probably because he is jealous (ouch!)

Anyway, lets see just how long it takes him to start something over on the samba about the numbers and about Lens head work.

Its all fine with me, every time he starts his crap all it does is blast peple to ALL my sites. Last week was the biggest we have EVER had for Video and book sales and a TON of traffic through the store site came from the samba on those threads when I peered at the site stats on Friday.

The more he bitches and moans the more people want to learn about what he is complaining about- then they go to the site, read, learn and become intrigued.

Dans BS post will ALWAYS be based on hearsay and opinion. He will NEVER have first hand empirical data and will never have any experience with the same car with TI and TIV power. This is due to his closed mindedness and backward approach to life in general.

So when you read this Dan- Thanks a million man... You keep me on my toes and keep the TIV drama going with your every negative breath- Too bad you can't post to the STF, because you acted like a child here as well and ended up BANNED!

We have a special little suprise for you, and I PROMISE you are going to love it.

raygreenwood · Post by **raygreenwood** » Tue Jul 26, 2005 8:34 pm

Thanks for the info HAM. I know Danimal is still around.....I got into a conversation on the FI forum with hime about a month ago. It had to be him. Same old lame sh*t...with no experience to back it up. He slipped in an article on a 1986 honda racing motorcycle head to back up his belief that all injectors should be placed upstream.

Might work well at 15K rpm...but just not quite as nice on the street. The also failed to notice the engine had twin injectors...both high and low...for low and high speed atomization. Didn't even bother reading what he posted. I just quit replying to the thread when I figured out who he was. Ray

Post by **sparkmaster1** » Tue Jul 26, 2005 8:52 pm

Just like old times. Danimal making a fool out of himself.... Tim

John W. Kelly · Post by **John W. Kelly** » Tue Jul 26, 2005 10:27 pm

I don't think it takes Einstein to figure out the t4 is a superior engine to the t1 simply because the engineering is more modern. VW designers didn't get paid to go backwards. The way I see it the t1 is more popular because there are many, many more produced. The small block Chev isn't the most technologicly advanced motor ever. It's the winningest race engine in the world because there are millions around and are of sound design. The more produced, the more R&D.

moggy · Post by **moggy** » Wed Jul 27, 2005 2:45 am

MASSIVE TYPE IV wrote: Its all fine with me, every time he starts his crap all it does is blast peple to ALL my sites. Last week was the biggest we have EVER had for Video and book sales and a TON of traffic through the store site came from the samba on those threads when I peered at the site stats on Friday.

The more he bitches and moans the more people want to learn about what he is complaining about- then they go to the site, read, learn and become intrigued.

The down side is, unfortunately that's exactly what happens to his site too

(and he knows it) which is why I think he does what he does to perpetuate the post, cos he can't be THAT stupid......surely

.
.
.
.
.
Can he?

The only 2 saving grace 's are:

1. Every time he does that he is also promoting the T4, as at the end of each one of those T4 v T1 threads the conclusion always seem to be T1-good for drag racing, T4-better for EVERY other application.

2. The other thing is Dan always comes out of it looking like an Arse!!!!

vw_chuck · Post by **vw_chuck** » Wed Jul 27, 2005 9:02 am

Len the heads flow better but why the poor HP/Cubic inch output when they are hotrodded?Alot of them are over 2300 cc and they make less power then a 2332 type 1? I don't get it. There must be a weak link there somewhere. Fix that and you may have something.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Wed Jul 27, 2005 9:09 am

It's not poor... Its just what we want.

We just don't care about, or tune for a narrow powerband capable of only hi RPM use...

Len and I both concentrate on strong midrange engines that are absolutely tame on the street when need be and also very power filled.

While many think my 3 Liter project has not been productive, they have not driven it and felt its 800 RPM idle and power than is on from 1,000 RPM. Creating an engine that doesn't need to be "Pushed" to generate power is a key that en and I have been striving for from day one.

The 2300 TIV makes its power solidily without coming to life at 4,000 RPM and being misbehaved down low- None of the guys that compae graphs and numbers without driving one will realize that- its impossible to comprehend until you are in the driver's seat.

If I had my emphesis on drag racing and making peak numbers the outlook would be much different along with our approachs to the goals- We are not.

HAM Inc · Post by **HAM Inc** » Wed Jul 27, 2005 9:46 am

VWChuck, I understand what your getting at, but you have to compare apples to apples. Jake and I have collaborated on high speed, high compression, normally aspirated t4's that produced well over 100hp/liter that have a nice broad power band that doesn't start until 5000rpms and runs to just under 8,000RPM's using all O.E. components. But this obviously isn't practicle for the street.
For the aircooled enthusiast that wants a good idling 180hp daily driver, but doesn't want to go in to the engine every 5,000 miles (or less) the t4 is perfect.

A beefy aluminum case that can support the cubes AND the torque, O.E. heads that can be modified to deliver the required flow without imbalanced port ratios and a thriving aftermarket that offers something for everyone.

And for the record, if only O.E. components were used in a build off, the t4 has the ability to make torque than the t1,(remember power is in the heads) even staying at 1600cc's. And if no size limitations were imposed the t4 with O.E. components can go WAY larger than the t1.

Understand that I love the t1. In the 70's and 80's I won a lot of circle track races driving cars with my fathers t1 powerplants. This isn't a Republicans/Democrats thing. It's just that VW designed a couple of different aircooled engines and the second generation is more modern and offers some advantages that the first generation doesn't. Isn't that the way it's supposed to be? I believe it's called progress.