Its easy to say from the keyboard, but are you curious to see if the power goes up after fixing the leak on the hta88?

 

I am somewhat curious, however some other thoughts have been percolating in my mind

The most important one is that when one part of a turbo charged system is at its limits, its hard to significantly increase power production by aiding air flow through the head, its just a simple fact.

In order to do meaningful testing, it is important that I have a system with plenty of head room to allow new parts to shine if they enhance VE. With a turbo operating at its limits its starting to do strange things when those wastegates close all the way shut - the power is droppping even though boost is climibing. This behavior reminds of of stock turbo STI's - when you go EWG and start raising the boost at a point when you close the WG totally the car drops in power becuase the turbine wheel is just too small to allow the exhuast to flow properly and you get excessive back pressure.

Al

 

So you think the turbine wheel is not optimal for the turbo? Or the turbo is not big enough to see the benefits of this head?

 

I think this turbo is only good for 800 whp on a 2.0 L Evo

I don't think that changing other parts of the set up will yield any power as I was able to achieve max power with the set up I had

This is all a theory and remains to be tested when I re-intsall the Gt42

(There is a part of me looking forward to once again feeling the top end of a Gt42)

Al

 

I would say so... I have not been in a gt42 that was properly setup..

 

The only way that intake velocity can push the exhaust back pressure is when the piston is 365 degrees from TDC. Intake and exhaust valves open at the same time, at approximately 0.060 lift depending on the camshaft. At that degree, let's suppose that we have 20 PSI of boost, the intake runner as a speed would create 32 PSI while the exhaust back pressure is 55.5 PSI. Inside the cylinder it's 22 PSI. The velocity of the intake port is only 67 feet per second. So I can not understand how your "high velocity theory" can fill the cylinder when we a 23.5 PSI difference working in the opposite direction of the flow of air.

I'm not sure if you know but the EVO 5/6 has an even larger port than my ported head. So even Mitsubishi follows the same theory...

Evo 4-9 port sizes are the same. From the ones I have seen.

Using your example as numbers from stock head. When you change to ported head that increase volume in runner and slow the 67FPS to 62 FPS during overlap. you would loose the ability to fill cylinder more effectively since you are being hurt more during overlap period. Air doesnt flow one direction in the intake port. It cycles back and forth. making the port flow well in the filling direction and poorly in the opposite direction is sometimes easier to do with smaller port. larger ports always flow very well in wrong direction. Thats why I stated earlier all this discussion would be better suited if we had back pressure numbers to look at. Again this is a 2000 word reply condensed to 200 words.

Problem with your theories and understanding of how the engine works is you over apply them. For instance your theory is lowering back pressure will always have a positive affect on making power. This application of your theory is simply not true. Al tested the larger back housing when the stock head was in play and it did make less power and spooled too slow. I personally have tested larger back housings on some of my setups and have lost power and spool. back pressure is bad during overlap period all the time , but there are far too many other things happening to say it will always produce more power in a system. In reality is is quite easy to reduce the turbos ability to power the compressor.

Another area where I have seen a misapplication of a theory is exhaust size on turbo car. Most simply state to install the largest pipe size your ears can handle. This simply is not always true as well. It is possible and I have seen it on my own cars is to have smaller exhaust size (IE 2.5 vs 3.0) that crates far more torque. It is common knowledge on N.A. car the too big exhaust will kill power. The correct size is when the exhaust pulses pull on each other. This effect is also true in some turbo setups. I have replaced 2.5 exhaust on one of my cars (excited at gaining more power) and left with 3.0 exhaust and huge disappointment from the loss of torque.

 

Well, finally I found some time away from work and family to get to work on the car

The head is perfect - the leak is from the rings

The bore still looks brand new

Tomorrow I plan to get the car up in the air and slide the piston out and take a good look at it

If all is well with the piston, some new rings and I will be back to testing later this week

Al

 

Al-

What method did you use to determine it was the ring?

-E

 

I used a Matco leak down tester

I took off the intake and exhuast and determined the head was 100% tight

I closed all valve cover vents and found the air was leaking into the cran case by piston # 1

The bores are 100% round and undamagec - no cracks

It is either a rin or a ring land

I will have it apart later this evening

Al

 

pm'd

 

Man, I tell you those Buschur short blocks are simply totally amazing

I have about 3 trips to the track and countless dyno pulls on this motor and it still looks almost totally brand new

I cannot determine what the cause of the leak down was / is becuase everything looks 100% perfect in the bottom end

The rod bearings look perfect BTW

I am thinking that perhaps the rings spun around nd just lined up with the gaps in a row - its odd becuase the rings - pistons and all looks perfect

Just in an over abundance of caution I am going to order a new set of rings from Buschur Tomorrow just in case

I don't have my camera with me but will post some pictures tomorrow

Al

 

You just got to admire Al's love for Buschur products, even when he has an issue he is still thrilled...

 

Well with this kind of power level usually when you have "an issue" you know about it and you know about it quickly - I have tossed a few rods in my day and when they do you have no doubt as to what went wrong

In this case, it seems that either a ring has lost some of its tension and not holding good compression - or - perhaps one of the bores has shifted and the clyinder is not totally round. Either way it is no detriment to the fine product that Buschur puts out.

When you are making 200 and up whp per .5 L bore size you are going to have to stay on top of your game when it comes to maintenance - no doubt about it its a very high output engine.


I have found that I actually enjoy the wrenching, testing and fixing part vastly more than the actual driving part. I love the simplicity and clarity of a purpose built race car which is devoid of all non essential parts. A clean, well sorted race car is an object of art and a total pleasure to work on and repair.

Al

 

You definitely have the right attitude Al - some people are quick to bash when something goes wrong, these people should be driving stock EVOs, lol... I really do admire you sticking with your peeps and what you're doing!

 

Exactly. Headwork is really important for pump gas power. It is less important on somehting like Q16, where you will probably be pushing the map of the compressor to its limits. Actually, all VE mods are like that (nice headers and big turbine housings).