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  #46  
Old 29-08-2017, 09:52 PM
franky franky is offline
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Originally Posted by SKiddell View Post
Running open trumpets on an L series can be bad due to drawing in dirty air full of dust, dust sticks to cylinder wall and makes and excellent grinding paste

Open trumpets also mean that your pulling in very hot air (in excess of 80 degrees) hot air into an engine is undesirable (its less dense and can promote detonation)

In tests (back to back dyno) we found an increase of 17 HP in some parts of the curve when using an airbox versus open trumpets....reflected pulses anyone !!!!! no, didnt thnk so.

And most Samuri's use open trumpets because that was the thinking of the time.....back before the asteroid strike when dinosaurs built engines

Oh and they sound good
I know a guy who built an airbox for a bike designed around the frequency of 2nd and 3rd wave resonation, I couldn't keep up but I just remember that its based on port size and rpm operation.

Generally an airbox will always make more power.
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  #47  
Old 29-08-2017, 10:50 PM
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Originally Posted by Mr Ex Jnr View Post
Right so would you sugest getting filters for them or a open air box with one filter at the front some where

Or keep it period the engine been like this all my life so I dunno what to do

Also my dad took the choke off it aswell runs nice without it just bit of a thirsty zed but I fort webbers were

I am thinking of 're building carbs for a start

It'll certainly go better with an airbox and cone filter out in front of the rad. Won't sound as good or look period as you say.
The airbox won't fix your economy and nor will a short session on a rolling road. To get the best performance and ok economy it's either £1000s on RR time or get an AFR gauge and start learning how the carbs work and you'll be able to make decent improvements over time as you learn. There are some good books around.
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  #48  
Old 29-08-2017, 11:20 PM
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Right I understand I'll keep my eye out for a air box go over the triple webbers and I just need learn how to tweak the carbs need to man up and have a play
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  #49  
Old 30-08-2017, 08:57 AM
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Right I understand I'll keep my eye out for a air box go over the triple webbers and I just need learn how to tweak the carbs need to man up and have a play
Mike used to do the air boxes, it might be worth asking him if he still does.
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  #50  
Old 30-08-2017, 09:33 AM
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Any cold air induction system will give you improvements in power as the engine bay air can get pretty hot. At very slow road speed and stationary the gains can be up to 5%. Once the car is moving and your really on the loud peddle, the engine bay temp should reduce dramatically with good airflow so the gains due to reduce charge temps will not be as high. Other gains can also be had from a well designed plenum. A superb stating point when looking at building an airbox are the old ford cosworth designs. These are quite complex but when you understand how they deal with presenting the correct amounts of air to each individual trumpet, it makes good sense.
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  #51  
Old 30-08-2017, 09:38 AM
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Mike used to do the air boxes, it might be worth asking him if he still does.
Mike at mjp
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  #52  
Old 30-08-2017, 10:24 AM
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Mike at mjp
Yes
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  #53  
Old 30-08-2017, 10:33 AM
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Right I'll give him a ring this week
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  #54  
Old 30-08-2017, 11:09 AM
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Something to be aware of, quite a few engines are using long velocity stacks (good for torque at the expense of top end HP) a cold air box won’t fit over these and if it did it would restrict the flow.
We found that the shorter stacks 60mm and below fitted ok, this will move torque and HP around the curve a little......generally shorter stacks lift the power up the rev range as they shorten the inlet tract, longer stacks increase the overall tract length and increase torque at the expense of top end power/revs
We use adjustable length trumpets with settings for max torque and max power.....tuneable induction tracts ....now if we could just automatically adjust them based on rpms and manifold vacuum we could sell it, we could be millionaires Rodney.....oh wait that's been done before, damn….
Just to answer your question as to why some race cars use open stacks
Some engine setups e.g. period F1 cars of the 50's and 60's had no bodywork in the way and they were open to air, with a very direct path from stack mouth to valve head....later thinking would use a ram air induction system to "push" air into the stack mouths
On race Z's well its horses for courses, race Z cars such as Big Sam or the Four ways blue monster don't do many miles and the engines get refreshed more often than road cars so the dust ingress/bore wear thing isn't so much of a problem, but as mentioned our (Pete and my) decisions are true back to back dyno based tests and personally, I wouldn't run open stacks....ever, mainly due to reflected pulses off the bodywork and heat sapping power and possibility of detonation.

Each to their own though.
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  #55  
Old 30-08-2017, 11:38 AM
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Quote:
Originally Posted by franky View Post
I wonder how many of those people with issues have had their car on a rolling road and gone through a full proper setup?
Yep, I did that.

Quote:
Originally Posted by Rob Gaskin View Post
Yes and do the people 'tuning' have all the knowledge/jets etc.

Anyway I will - already discussed it.
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Originally Posted by franky View Post
I think that's more than half the trick, finding some where that are knowledgable and comftable in setting them up.
I used Motorscope at Northallerton, http://www.motoscope.co.uk/rolling-road/

and I wouldn't hesitate for a minute in recommending them, since it went there nearly four years ago the carbs have never needed touching, compared to the idiot that was recommended earlier in my ownership by a certain North Yorkshire Z specialist, who for an alleged expert, had no idea what he was doing and I am sure caused more problems than he solved.

Quote:
Originally Posted by Rob Gaskin View Post
I've heard of 20 mpg.

All 3 of my Zeds have done very high twenties and come to think of it so did my 370Z.

I would hope to get 25 out of mine with triples - we will see.
I get 25- 28 Rob depending on how I'm driving from the set up I sent you last night.
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  #56  
Old 30-08-2017, 01:38 PM
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Well av orderd some foam filters for now 30 pound for the 3 it say so all good and in the mean time in keeping eyes out for a air box seen them on mjp website just don't like the price haha looking down standard air box route and modify to for the webbers got few good ideas to try out see what improve it then take from there
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  #57  
Old 30-08-2017, 01:39 PM
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I haven't actually worked it out for my self but it is first got me to oulton park and back and the hotel I stopped at on 50 pound and I drive it steady and fast i filled it up again when I got home as it was empty did 130mile round trip

Last edited by Mr Ex Jnr; 30-08-2017 at 01:45 PM..
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  #58  
Old 30-08-2017, 02:00 PM
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Back of a fag packet calcs ...

£50 - say 10 gallons ... 130 miles - 13mpg ... christ that is poor!

My old fastback had a Quickfuel 750CFM drag carb on it and I got 12mpg - and that was a 347cu in stroker ... one of the reasons it had to go. I once went from PBoro to Bury St Edmunds and back and it cost me over £80!
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  #59  
Old 30-08-2017, 02:09 PM
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So my dad was right but that was driving hard at times I h pushed it over weekend a lot more than normal so av got a few ideas and things to tweak on the old girl
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  #60  
Old 30-08-2017, 02:25 PM
franky franky is offline
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Quote:
Originally Posted by SKiddell View Post
Something to be aware of, quite a few engines are using long velocity stacks (good for torque at the expense of top end HP) a cold air box won’t fit over these and if it did it would restrict the flow.
We found that the shorter stacks 60mm and below fitted ok, this will move torque and HP around the curve a little......generally shorter stacks lift the power up the rev range as they shorten the inlet tract, longer stacks increase the overall tract length and increase torque at the expense of top end power/revs
We use adjustable length trumpets with settings for max torque and max power.....tuneable induction tracts ....now if we could just automatically adjust them based on rpms and manifold vacuum we could sell it, we could be millionaires Rodney.....oh wait that's been done before, damn….
Just to answer your question as to why some race cars use open stacks
Some engine setups e.g. period F1 cars of the 50's and 60's had no bodywork in the way and they were open to air, with a very direct path from stack mouth to valve head....later thinking would use a ram air induction system to "push" air into the stack mouths
On race Z's well its horses for courses, race Z cars such as Big Sam or the Four ways blue monster don't do many miles and the engines get refreshed more often than road cars so the dust ingress/bore wear thing isn't so much of a problem, but as mentioned our (Pete and my) decisions are true back to back dyno based tests and personally, I wouldn't run open stacks....ever, mainly due to reflected pulses off the bodywork and heat sapping power and possibility of detonation.

Each to their own though.
What was the chronological order you developed the engine in and results as you went along?

I only ask as you've gone as far as anyone on this forum has with an NA L-series
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