royal

Hi guys,

I've spent the last few days reading through some of the great porting threads on this forum so firstly many thanks for that!

I've got a specific query thats covered to some degree in other threads but I wanted to ask as I've seen a few contradictory posts.

I'm building an FD drift car to compete next year. I've got a manifold from my 13b REW out of a cosmo that broke a seal and killed one side and other bits from a few spare engines I've bought. I'm doing my first port job so reading as much as possible. The original porting was for when the engine was running 550bhp and was a very big streetport with lots of overlap. I've now got an Apexi rx6 turbo kit and aiming for 400ish bhp but really want to concentrate on not losing low and mid rpm torque even if its at the expense of high rpm power. For this reason I don't want to use the existing porting.



I read various things on the forums and also the turborx7 site with the racing beat port figures and I got it in my head that I could open the exhaust port nice and early and not play with the closing time all that much. Theory that it would help spool the turbo sooner and not kill low/mid driveability by having late closing and too much overlap? I figured I didn't need to close late as I didn't want to move the power band upwards.



I did the exhaust ports but after reading more on here and talking to people I think I've gone too far down. I decided to measure the timings but need to do it again as I'm not sure of my accuracy. The exhaust opening time was 84 degrees BBDC which is the same as that stated for the racing beat street ports which seemed ok. I then measured the still almost stock closing time (gone up maybe 1mm) and got 58 ATDC which is out by 10 ATDC from the stock 48 degrees (note the protractor was moved between measurements so not consistant, I did measure several times though). So now I'm worried my figures are out and I've actually gone way to far early opening on the exhaust! I reckon I've burr'd down 3-5mm where as looking on here most seem to only do 1-2mm earlier opening on the exhaust? Any more recent research I read says that you can open the exhaust a lot earlier than most people used to think many years ago but I have no experience and many people are warning me against opening the exhaust earlier?

What I want to ask is; in your experience physically roughly how many mm do you take off the bottom of the exhaust port if you were to open it early at 84 degrees BBDC instead of the stock 71 degrees?



Any help really appreciated , Dave.

fc3sboy1

a bit confuzed. you have a 13brew from a third gen or a 13bRE out of a cosmo? the rotor housings are slightly differnt and the intake manifolds are worlds apart and the stock twin turbos from the 13bRE are smaller then a REW.

royal

Sorry my mistake. I was just trying to give some more info. I have a blown 13bRE cosmo engine in my FD. I've now got it in bits porting it as above. I knew the manifold was different but didn't realise the housings were. As I'm not using the RE housings I guess it means I'll be rebuilding a 13bREW FD engine and using the manifold from the cosmo RE assuming this is a recommended thing? if not then I can just use an REW manifold I have here?



I'm not using twin turbos.



I'm porting FD REW housings and need to know if I've gone too far down on the exhaust opening and if anyone has any experience of doing this? My thinking is the useful part of the power stroke doesn't last that long so its ok to open early but have I gone too far by going down 3-5mm?

royal

Anyone? guess I'll blunder on!