I had to read this a couple of times after my head stopped spinning... I too, really would like to dyno test this head and any others (it's much better than work!), and I have the use of one 10ft away from where the flowbench lives (if only you could all hear what I listen to when I'm testing heads, close yr eyes and imagine an open induction 2.3 XE being set up next to yr left ear ! ), but dyno time costs money. To set up the dyno cell with k-jet to test a standard engine for example would take a lot of work (I've already asked !), it could be done, but whos paying for it ? Testing a modded engine on carbs or t/b's is a possibility in the future, but again, it'll depend on cost, and when a complete suitable engine is available. I have two 1800 8v engines to do, both will have flow tests of the head and complete induction (sorry, old fashioned carbs again) and at least one will reach the engine dyno, but both are known quantities on the rollers, so I'll be able to relate some flow to power, but it may not please all of the people all of the time. But even this is much more than many so called "pros" bother to do, certainly in the VW world. I dont know many head modders that dyno test just the head, and even that value will change depending on the cams used (x cfm @ x lift), it's normally as part of a package. All I'm testing at the moment is airflow, and how effective certain mods are. Apart from Neal H, I dont believe anyone else has even gone this far (in fact, even Neal only tested at one fixed flow rate, I expect due to time/testers constraints) and we're only just starting to scratch the surface. It's still a learning curve for us, your seeing what I'm seeing.
That is indeed the aim, pub talk hp numbers is'nt what I'm at, and I wont rest until I achieve at least what I think is an acceptable result for the use it's being put to.
hahaha. No reason to have it spinning . I am cool. The formulas used to equate airflow to BHP would give and the approximate BHP potential without the interactions of everything else! Just like I could use similar formulas to estimate the BHP airflow potential of a turbo compressor from a compressor map and injectors from their flow@pressure and duty etc. But on the engine in real life you still have to run up to this point. The simple formulas cannot work out this cumulative. A typical comment would be, "an engine with a 200hp head and 210hp injectors and a camshaft that could 'gain' another 15 hp had to 190 hp on a dyno with a good calibrator when it was 150 before at another dyno". Even though the original source of the values are unknown, the trouble with this method of reporting back engine performance increases is that it is very vague as it does not reference to a specific rpm point, says nothing about how this modded engine will behave in a when you attempt to lightly tip in after a part load cruise or when you accelerate moderately (not at WOT) to 5000rpm (when the horsepower peak is at 7000rpm) and certainly does not say when is the point of maximum cylinder filling i.e. when your torque is the highest. This is why the books that suggest approximation formulas to equate bhp, only do so after performing validation on all components such as the head data you are researching, to the engine dyno or chasiss rolls to validate how they would work and when they would work. So if there is a curve for BHP with modifications and without, then an engineer or someone who is building a similar engine to specific requirements, can back calculate how that engine would accelerate a chassis based on the torque. I should also point out that there engines modifications that do not increase BHP but will transform the way the engine behaves anywhere under this point. Its not an ABF motor but it is better than nothing and will evaulate your work. Yes this will be very good, both practical and scientific. I think this it is very good idea to collect this data. Even more to real life when you demonstrate how it made the engine breath via a torque/horsepower sweep.
My head has been to shed twice and came back second time looking alot better ported i'll find some pix. 10 Years in between the working being done.
Thats development for you. I have access to a head alleged to be TSR supplied, but bought used by a friend, so could be anybodys to be fair, unless there are stampings on it. I may get the chance to flow it at some point but not sure about posting results, maybe a bit unfair on someone who makes a living from it. Until the final seat cut's are done on mine, I'm on the fence regarding how big the actual ports need to be. So far, I think all that could be needed for road type use is decent seats and blended into enlarged throats. I'd like to test with a standard 16v inlet to see just how much is knocked off either standard or ported... job for another day.
Interesting, I've always back-cut the valves whenever I've "cleaned up" a head when doing a head gasket or re-build and I always felt it "pepped up" the feel a bit. How aggressively did you back-cut and did you reduce the stem size too? (a picture perhaps?) Cheers Simon
No stem size reduction as I dont want to take the chance of a valve head dropping off, any flow gains tend to be lost with hole in a piston... I'll sort some pics in a day or so, but it does'nt need to be critical, just a removal of the edge fron the seat to the back of the valve does a good job.
Put a pic up if you like - I could give you a fair idea if it's a real one. You know what you're looking at though, so I don't expect it's a rough old homemade job. Alternatively, have a look at the pics in the Cylinder head group buy thread and see if it looks like the same work. They're not stamped or marked anywhere. I've seen some right old tat pretending to be TSR's / other shed customers' heads.
heres one we made earlier I can laugh about it now, after several years of therapy......not much left of that tuned valver that day I can tell you (dropped a valve at rather high revs) [/IMG]
Bad luck Rob, it's no laughing matter when you hear the "death rattle" tho... The 16v head is back from having the guides and seats done (another superb job from my man), off to do the final bottom cut blending then it's on to the flowbench... gulp.
