2tg head flows

[NME308]

Good news indeed. Cant wait!


Cheers,
Jason

[MorGo]

No need for retards;it should be run just the advance it likes! Late ignition just melts plugs and exhaust valves.It is not more safe than correct advance.
At 7:1 comp you can run any advance you like (but something near 40º would be close)

[NME308]

No need for retards;it should be run just the advance it likes! Late ignition just melts plugs and exhaust valves.It is not more safe than correct advance.
At 7:1 comp you can run any advance you like (but something near 40º would be close)

I hope this is just a language barrier making it sound like you are suggesting 40deg ignition would be safe to use at 29psi boost???
At 40deg timing with 29psi boost on 95 octane pump fuel the exhaust valves are not going to have a hope in hell of melting because the cast factory pistons will break first... I have run 7:1 comp long enough to know where my engine timing is safe thank you...
Maybe it is my anti-lag launch tune you don't understand??? Anti-lag is only run for 2 or 3 seconds to get up on boost fast for drag racing only.

The MSD ignition module allows me to set the 'correct' timing reqired for the different engine conditions. The MSD terminology is retard for this process i.e. you set the total ignition timing manually on the balancer and then use the 'retard' to create the ignition map. It works opposite to mose EFI style systems where you set the minimum timing you wish to run and create your timing maps up from there. I hope this is the explanation you need.

Cheers,
Jason

[metcap]

On your 7.1 comp you can run 37deg right up to 0.6bar?! when do you start water injection? I've a calculated comp ratio of 7.4:1, on hard throttle launch and my knock control is pulling degs off if I leave it at anything more than 30 deg. What do you think is not right? No wonder I'm building speed too slow.

[MorGo]

Well,if you know what the engine likes why you ask??

[NME308]

On your 7.1 comp you can run 37deg right up to 0.6bar?! when do you start water injection? I've a calculated comp ratio of 7.4:1, on hard throttle launch and my knock control is pulling degs off if I leave it at anything more than 30 deg. What do you think is not right? No wonder I'm building speed too slow.

Yes I run the 37deg up to 0.6bar.
I start the water injection at 15psi boost.

Can you describe more fully the situation? You feel your engine lacks urge but is it only before boost onset? Is it up until a certain boost level then it takes off like you expect? What are the specifics of your turbocharger including exhaust A/R?

When I had an exhaust turbine with an A/R size too large the engine was totally sluggish! Off boost response was quite marginal and boost onset was quite high in the rpm range. Even when boost did start there was no urgency as the boost just built in a linear fashion with rpm so there was no instant torque hit to drag the engine up quickly in the rpm's! Changing to a small A/R (or in this case blocking one of the two scrolls) has given me back throttle response and plenty of engine urgency!

A couple of things to keep in mind are my engines intake tract is quite restrictive and no porting. If you have something well designed and free flowing your engine could be making much better cylinder pressure than mine for each psi boost you put in. This will immediatly dictate a different ignition strategy for your engine. Of course your cam profiles and cam timing will play heavily here as well as this influences the dynamic compression the engine sees while operating.

Now a bit of theory here - the formula 1 guys in the turbo era were running 6 & 7:1 compression engines and documented that (I'll cut it down in my own words) the BSFC starts out woeful and improves as the cylinder pressure is raised with boost pressure. The thermal efficiency of a low comp motor well is down on a high comp example until you get it up on boost and the cylinder pressure brings the efficiency back again. Each point of compression is worth 3.2% power to an engine (properly tuned). Each psi of boost is worth 3.5% power to an engine (once again properly tuned). For your 7.4:1 compression motor to equal the power from an otherwise identically built 10.4:1 compression motor you need 3psi more boost at any given point. Here is however the beautiful thing: your 7.4:1 compression motor will need WAY more boost to equal the cylinder pressure of the 10.4:1 compression motor. As an example at 15psi with 10.4:1 comp it takes the engine with 7.4:1 comp 27psi of boost to equal the cylinder pressure. So for any given fuel (read that as identical cylinder pressure situation) the 7.4:1 comp is up 32% power potential over the 10.4:1 compression example (7.4:1 comp is down 9.6% for compression loss, and is 42% up for extra boost to equal cylinder pressure).

Why did I sprout all that? You will need to be putting quite a lot of fuel into that engine until it is getting decent boost pressures. What are you running for ecu? I do not know of too many aftermarket ecu's which support knock control (especially not cheap ones!). On the flip side I know of bugger all factory ecu's which will know how to properly cope with 7.4:1 compression, porting, and big cams etc... Since an engine relies on mainly only a few basics including fuel and ignition and you get knock with more ignition and still lack the urge you want can you do say a 10% across the board fuel increase with your ecu as a test?

Cheers,
Jason

[J-M kujala]

There is also good and "Bad" heads from early 220 and 222 numbers..

just take some photos at most bad 2TG ports what i have seen.. this is one of my 2TG heads what is laying around garage.. ports are far away at correct places..

SO there is differences between heads a lot..

[metcap]

Mine's just a backyard build so nothing fancy, basically just a dinosaur era t04e with .68 turbine and I've a megasquirt controlling fuel and spark. At the moment the kick in the pants feeling is not quite there coz boost really builds up almost at 4000rpms. Well I've not tried dialing in more fuel before boost onset coz I'm thinking that might hurt criusing fuel ratio, thats something to try though.

[metcap]

There is also good and "Bad" heads from early 220 and 222 numbers..

just take some photos at most bad 2TG ports what i have seen.. this is one of my 2TG heads what is laying around garage.. ports are far away at correct places..

SO there is differences between heads a lot..

that looks ugly, I've not looked closely at my 222 head but hope to soon to make some backyard port job. looking at those pics is it possibe to recover those ports?

[J-M kujala]

Can make head what is usable, but make it "good" maybe only head with all out, but still need some welding behind valve seat. There is ~2mm step behind valve seat at other side of the ports. That may need a fill with small welding operation.

Thats why the head is empty and used for only parts..