PSI verses Timing Advanced

[Bernardd]

Hi,

 

I been reading some post where TonyD and other are talking about not needing to run higher turbo boost pressures, but to allow the head to breath more.

 

But I have not heard anything about spark advanced verses boost pressure, for example,

 

lets say I'm running 20psi, but I can only run 10 degrees max at high RPM,

 

would this give more power than say running 12 psi running 35-38 degree at the same RPM.

 

Nigel

 

If you make more power at the lower boost level and more timing you need more octane or better charge cooling or the turbo is running off the map at the higher boost level. I had the same situation with a 123.9 trap at 22-23psi and x timing. With 26psi and x-7deg's timing I could only muster a disappointing 119mph at the strip. If I had stuck with the old setup I would have started to add a degree of timing each run until I reached the point of little or no gain.

[rossman]

Rossman, did you notice any difference in power or driveability? At this point I'm thinking my time and money is better spent elsewhere....

 

I wish I had data for you but I'm still building the car.

[softopz]

Very Good read, I am glad I did my own little porting at home. But I have some questions. I ported my head about 2-3" as deep as I could get with a dremel and polished it I matched it just under the manifold gasket removed the casting pattern line etc. I think there was a 3-5 mm increase in Diameter. I also did the Turbo manifold and intake manifold port matched it to the head. However My question is my valves and cam are still stock am I moving / flowing more air into it? How much hp/tq do you guys estimate I gained? I do feel a difference but I havent re-tuned the car till I get my wideband on. I Still have a stock T3 my block is .5mm over w/2.5" DP and 3" mandrel bent. My next mods are wideband and t3/t4. I'd really like to give my brother a run for his money he has a 3.1 stroked forged bottom end gt35R , sds , methanol running 17 psi making 340 hp stock head/IM and EX manifold. After readign this im really think I should re-invest into the head Maybe bigger valves and msa stage 2 turbo cam.

[Tony D]

Frankly, from what you described, you did absolutely nothing. Double that for being stock cam and intake manifold.

 

Seriously, the port work is in the bowl under the valve, not in 'port matching' or making the runner bigger. Quite the contrary. Matter of fact I have seen ports that flow 215cfm+ on the intake on runners sized to the FIA Homogolated 35mm diameter dimension.

 

Really the trick is to get the flow WITHOUT a runner diameter increase on the head. By that point, it's directional and velocity you are working on. Increasing the diameter of the port at that point (unless you started at 50mm at the triple manifold flange...) is the LAST thing you want to do!

[Noddle]

During my internet searching, I came across this page

 

http://alfaboxertuning.fws1.com/

 

it not directly related to the 'L' engine but has some nice information about porting in general,

 

I liked the pictures regarding the "inlet / exhaust port mods" as seen in this picture

 

Nigel