N/a 8V Max Performance...?

[onur205gti 3]

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[DamirGTI 327]

Valves look good exhausts , no point reshaping/undercutting the stem on them if they're OE two piece "weld on valves" , cos the surface is needed for heat transfer along the valve and in the case of thinning , the stem will crack apart from the valve head - too hot for such mod on exhaust valves .

 

D

[DamirGTI 327]

It would be interesting to see some port flow charts @ 28in.

 

Ditto Peter ,

 

Guy Croft had an complete article about 1.6 8v head porting/modifying , along with the flow charts .. aside from the head he also tested the OE inlet manifold . Sadly though , none of this articles aren't available on his website anymore

 

Might try to drop him an PM , if he still have the data and would be kind to share them .

 

D

Edited September 10, 2013 by DamirGTI

[Sandy 189]

I'm a firm believer in optimum valve sizes for an application. The pet theory put forward by most race engine scribblings and armchair experts, is that if you can run a bigger valve, you need "less cam". The thing is, you don't pour out a necessary amount of cam to get a recipe right, different applications respond differently to different cam lift curves and the way the changing curtain area relates with everything else that's going on. Simply filling a cylinder by pumping airflow, you can only ever hope to achieve maximum pump efficiency, which sits at around 90%, if it works really well. That's never going to be a reality with a head like this though, 2v, side-draughted and bathtub chambered; so the only way you can get decent cylinder filling is through pipe tuning to scavenge well and induce effective pulse tuning. Flow is of course important, but in my mind just as important as pipe tuning, mixture quality and a clean/complete burn. I can't see the sense in trying to maximise flow if it hurts the other properties.

 

I quite like the kind of engine I get with moderate valve sizes and fairly gentle long duration cams. The inlet/exhaust development and fuel supply/management deveploment I've done has allowed me to evolve engines built this way to be vice free and less aggressive (as in low valve acceleration/speed) cam profiles greatly help longevity, so the performance lasts. I've tried going the other way, with bigger valves and cutting edge cam profiles, only to find the power band narrows and peak torque reduces; quite the opposite I'm afraid to what popular theory (and DB) suggests. Perhaps I've done it all wrong, but there are many ways to skin a cat when it come to engine development, there's no definitive right way.

[DamirGTI 327]

Agreed .. just the head porting job (even if done very good) wont make the engine "fly" if the other aspects of engine tuning are left unmodified .. more to it , it can hurt the engine .

 

It's a well chosen combination of all the engine mods (along with the flowed head) which will make entire package really work/perform performance and durability wise .

 

D

[onur205gti 3]

What would you recommend for this spec using brain microsquirt???

[onur205gti 3]

I got friends with 8v cylinder head port polish and measurements based on the increase in the flow rate was increased by close to 70% of cfm ..

Edited September 12, 2013 by onur205gti

[onur205gti 3]

http://www.youtube.com/watch?v=EqNmqcT8OtE

[onur205gti 3]

Hey, I could not write for a long time we got 213 bhp .. We're still a little work on. Microsquirt v2, pulled some trouble I put a new reader gadget will update this weekend, thank you.

 

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[dcc 855]

Interesting would you happen to have the graph for bhp and torque and the setup of the rr? Nice figure for a 2138cc 8v engine.

[onur205gti 3]

No , no graphics

No , no graphics

 

Interesting would you happen to have the graph for bhp and torque and the setup of the rr? Nice figure for a 2138cc 8v engine.

no , no graphics poor dyno results

poor dyno resultssome parts have changed could be better...

opel corsa 1.7 DTİ Big Turbo 2260vk 214bhp

205 gti 175 bhp

Some parts have changed

Edited September 28, 2014 by onur205gti