I want to play a game.....

[morbias]

Apologies for going off on a tangent, but with regards to the exhaust what are your thoughts Steve on keeping the primaries 1 5/8 and then opening the pipe up after the collector? Would that act to speed up exhaust exiting the head as it flows into the lower pressure area after the collector?

[EDIT]Matt, if you're looking for an easy small power/torque hike why don't you just build an L26? You already have half the parts in your L24.

 

[mattbibbey]

Thanks for all that info, it's quite a lot to digest . I never claimed any kind of power output target, I only started this thread as a bit of fun. "Have a guess, win a naff prize".

Sadly I don't have the means to go out and buy a 2.8 and all the other things to go with it otherwise I'd go out tomorrow and buy a nice 3.2 stroker or something! What I'm doing, I'm doing because the car was in pieces anyway so I thought why not put it back together with the nice shiny things that I've had in the drawer for years. I'm not doing it for massive power gains, I don't do race events or rallies but I love a hard thrash every now and then. It's just for fun.

I got the cam from a friend at a good price and I don't think it's radical enough to make normal driving a challenge but I won't know until it's done. I can always go back. I liked the look and sound of the DJ exhaust system and that doesn't fit with the standard carbs. So really the triple webers decision was made by my boyish lust for that fantastic looking exhaust system. Then I thought I might as well follow up with some other stuff. This whole project hasn't been at great cost at all. Quite the contrary. Probably way less than half what you think it would. For my webers, cannon manifold and linkage I paid about £600 which considering they're new....

You've gone way too technical for me here. I knew when I bought the DJ system that it was considered to be a bit too big but I didn't mind losing some low down torque in order to gain the noise that I desired. To the purists, tuners and race engineer types on here, I may be serving up dinner to my dog but I'm not in the same league as you guys in either knowledge or funding for this project. I'm doing what I can with what I already have and I'll just enjoy it.

I am grateful for your contribution mate, I wasn't expecting such all encompassing criticism but that's what's good about open forums so thank you.

 

[mattbibbey]

Apologies for going off on a tangent, but with regards to the exhaust what are your thoughts Steve on keeping the primaries 1 5/8 and then opening the pipe up after the collector? Would that act to speed up exhaust exiting the head as it flows into the lower pressure area after the collector?

[EDIT]Matt, if you're looking for an easy small power/torque hike why don't you just build an L26? You already have half the parts in your L24.

Sorry buddy, I didn't see your post until I'd replied. I would do any of the above suggestions but I'm not in a position to do that at the moment. I budgeted for this and it's all sorted. In a year or so, I may be in a better position to chase a bigger engine but it's just not possible for me at the moment. I've already spent the largest amount of what I'd set aside for the car on the most important part to me..... the metal work.

 

[morbias]

Well I still have the crank and rods out my old L26 if you change your mind!

 

[SKiddell]

Apologies for going off on a tangent, but with regards to the exhaust what are your thoughts Steve on keeping the primaries 1 5/8 and then opening the pipe up after the collector? Would that act to speed up exhaust exiting the head as it flows into the lower pressure area after the collector?

An expansion chamber like that would work and has been around for quiet some time but perhaps only if the rest of the system was overly restrictive.

That broaches the subject of "back pressure" yet another subject that has become clouded with myth.

Mattbibby, I fully understand your on a budget and some of the choices have dictated the route, and the DJ exhaust is a nicely engineered bit of kit and good value compared with many solutions on the market.

But I would consider trying to raise the compression ratio a little, it doesnt need to cost the earth, typically 30 thou of a virgin head along with a felpro 1mm gasket will get you around 10.2:1
That extra point and a bit will pep the engine up considerably plus skimming the head will ensure a true flat surface, then you can take the valves out and make sure you have good seats but there is a warning, the bottom end needs to be in good knick as higher cylinder pressures will challenge the ring/bore seal more and find any weakness and could result in a smoky engine and or excessive sump pressure.

Are you going to use an adjustable cam sproket with the nice billet Isky cam ?

 

[mattbibbey]

I see what you're saying. The guy who is doing my head said he'll skim the head at no extra cost. I understand I'm looking for factory depressions in the face of the head as I have a feeling that it may have been skimmed already but I'll check this weekend. Aside from a skim, what else, if anything, is there in the cheap bracket to increase compression?

Cheers

 

[SKiddell]

Mentioned before is the Felpro head gasket, it compresses to 1mm, stock Nissan is about 1.4, doesnt sound much but every little bit helps and it will also improve the quenching as the E88 and the N42 heads are designed with emissions in mind so tend to be more of an open chamber rather than a performance biased closed chamber design
BTW dont get the head over skimmed, the 30 thou mentioned is on a virgin unskimmed head, over skimming a head is bad news on lots of fronts

 

[morbias]

An expansion chamber like that would work and has been around for quiet some time but perhaps only if the rest of the system was overly restrictive.

Interesting, I will put that on my 'further investigation' list (along with your airbox experiments Pete was telling me about yesterday). They seem like the best ways to optimize power without even touching the engine.

 

[bigblock]

Hermann von Helmholtz

Hello mr morbias,,,if you do get seriously interested in tuning do some research also on Helmholtz resonator tuning and maybe the guy himself.(my bad if familiar)Bear in mind it varies on style of engine and number of cylinder layout,,,an old subject, but still applicable today.Cant put up any papers but viz amongst others touches a little on the subject.Link,,starts on page 35 or 36.

http://books.google.co.uk/books?id=...e&q=helmholtz resonator plenum vizard&f=false

 

[morbias]

Thanks for the link, interesting that it mentions the plenum is most effective at controlling resonance at a specific RPM when the number of connected runners is less than 4. So maybe separate airboxes for the front 3 and rear 3 cylinders of a straight six would be an interesting experiment, though routing the intake pipes would be a pain in the ass. Also tuning the plenum size and shape in relation to the air horns you're using looks to be the key factor to getting the biggest effect out of it.

I've bookmarked a few formulae so I think I might have a play around with that at a later date when I have the time to spare!

And so sorry Matt for totally derailing your thread

 

[AliK]

Now that's the first proper TopGear substitute I've seen!!!

 

[AliK]

Oops wrong thread! Apologies :s

 

[SKiddell]

Morbias, if you want to read up on exhaust theory there a good item by David Vizard in our technical section http://zclub.net/forum/showthread.php?t=18716

I went to a seminar by him last year, well worth the money, no matter what, he's been there done that, got the tee shirt, worn it out and bought a new one.