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Decent camshafts are where its at for both na and turbo twin cam engines. So long as you can get exhaust gases not returning to the cylinder, bigger is better. 

The only thing you may give away is a little bit of idle stability with might be considered a pretty aggressive camshaft selection. 

The is a bit of a warning though, if you run a relatively small turbo you can't go too massive on a camshaft choice or you will run into reversion issues. But big a well flowing turbo / exhaust will be wanting for of big cams to match with a gain in spool torque and midrange over a smaller cam. 

 

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yeh,    cams in this have over 5mm/4mm  - in/ex  lift at tdc.   Chances are it wouldn't even idle on a single throttle setup

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@kpr - have you done a side by side comparison of your 151kw tune with the filter installed/removed? I'd be keen to see if there's any difference with the filter on. Also keen to know how much room you have inside that filter between the top of the trumpets and the inside of the filter element - it looks spacious compared to a domed pipercross/ITG. 

 

I also lolled at the way those silicone joiners jiggle in the high RPM. There's some serious pulsation happening above 5k or so. 

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Going back a few posts here but do you think the 6000rpm flatspot has more to do with the lengths than the diameter of the tubes? 

 

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1 hour ago, Truenotch said:

@kpr - have you done a side by side comparison of your 151kw tune with the filter installed/removed? I'd be keen to see if there's any difference with the filter on. Also keen to know how much room you have inside that filter between the top of the trumpets and the inside of the filter element - it looks spacious compared to a domed pipercross/ITG. 

 

I also lolled at the way those silicone joiners jiggle in the high RPM. There's some serious pulsation happening above 5k or so. 

Think i  tried it at some stage and wasn't any difference.  will try a back to back next time its on the dyno.  from memory its the biggest one 435x190x115. which i assume is od.   trumpets are about 75mm long.  so should have 25mm clearance.

 

37 minutes ago, Rhyscar said:

Going back a few posts here but do you think the 6000rpm flatspot has more to do with the lengths than the diameter of the tubes? 

 

You mean the dip at 4500 ish from the big extractors?   they aren't too far off the same length as small.  I did cut the big ones shorter not long after building them, and wasn't really much if any change. although was probably only 50mm or so.
also, the big ones didn't actually make any more power than the small ones up top, until i added the stepped section. 

once i'm finished messing around with the intake,  will try some more exhaust stuff.

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Yeah that’s it sorry. Maybe they needed to be longer? 

Agree it will be interesting to see once it’s all together with the new intake. What’s your goal max torque rev range you are aiming for? 

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maybe worth a try.  but  im more leaning towards 44.5 is just too big.     the step made more power, so tempted to try that on the 38mm's.  the stepped section will be getting pretty small and may cause a restriction  though.

no real specific area in the rev range im aiming for, what ever it likes really.  Tbh  goal already achieved  was looking for 150kw with good midrange power.   but why not carry on..     i know i could easily make 155kw+ with the parts i already have hanging around.  but would only be good for wank factor or a circuit /drag car. as would take a big hit in the low/midrange.

 would be interested to  overlay my power curve onto other 4ages making the same power.

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Have you done any reading about anti reversion chambers on headers / after headers? I know you tested an expansion chamber at one point, but I'm not sure if you've given these puppies a go. It sounds like the theory around stepped headers could serve a similar purpose to these anti-reversion chambers. They look like they could be fiddly to make though... 

There's quite a few open wheeler headers with these bits in them (high level like F2 and old F3 cars) and lots of chat in the big block speedway world too. 

anti-reversion-header.jpg.5ad03a528b956cd97e91c3cf33013619.jpgantireversion.jpg.c8b90e8310ca6df7882b4a436516a5de.jpg

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Yeah the step is the way to go. From what I’ve been reading they broaden your torque range by a good 500rpm. I think it would be worth doing a bit more work on the collector and the restriction straight after Which sets up the scavenging effect.

 

here are the headers on dads car 

38F30D1F-0D6D-46C3-B4B1-A880FC178F39.jpeg.03d5e95d3a5deb03b17e59be617dc81a.jpeg3665FAC5-FC47-477E-AD49-28E48762E536.jpeg.f102844a74525af53f9f65c7acac564a.jpeg

 

they were good for 140kw but is suspect they are a bit small for the 150 it’s now making. In hindsight we should have gone to 4-1 design as the range it makes power in has so many more variables such as cams and intake than just the header design and you want them to compliment each other slightly offset not all line up in the same spot. Making power is like building momentum (I.e. area under the graph)

Keen to see how far this thing can go 150kw is a lot. What compression are you running?

I’ll see if I can pull out a dyno graph of the old mans 20v. 

 

Edit: @Truenotchafter reading those articles in my build thread I realised my understanding of reversion vs scavenging effect was wrong.

I always understood them to be the same thing but they are quite different. the reversion wave (exhuast particles) travels at approx 300ft/s (this may change depending on cylinder/header sizes and compression) and the scavenging wave (sonic) travels at 1540ft/s (this is a number a smart old Barry once told me to use with expansion chamber distance from exhaust valves) 

I guess the trick is to set up the lengths so you don’t end up with a flat spot caused by reversion but still get the benefits of the scavenging. 

I wonder if the reversion chambers would effect the scavenging wave too? 

 

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Nah not hytechs we got them acoustically designed by Harris pipes in Chch then built them ourselves. This was a about 5 years ago before I had learnt anything about this stuff. 

Agree that hytechs are the best for Honda’s and so cheap too. 

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@Truenotch    Those chambers look interesting.   haven't tried anything like that on the runners.  but definitely going to put it in my list of things to try.     Have something similar after the collector to my exhaust.    black part being 2.5" collector.   red the cone and green 3" exhaust

ex2.png.e9dc213cc395c0510a4080319776fe9e.png

can see the cones on both extractors here

2.jpg

@Rhyscar

I have a short merge for the 44.5's  with same 2.5" collector.   it didn't seem to have any effect. but was pre dyno,  so possible was some very minor differences.  will likely revisit the megaphone setup also.   should be gains to be had, but not expecting a lot like on the intake side.
Its running  somewhere between 12.5  and 13:1   compression.  was going to go for more on latest build but cheaped out on new pistons.  could skim a little more off the head. but  would likely have a negative effect.  as its all pretty tight and would have to adjust cam timing to gain piston to valve clearance.

 

Found a dyno  run to overlay  from here

https://motoiq.com/extreme-engine-tech-technosquares-monster-naturally-aspirated-toyota-4ag-part-3/

 1800cc engine,   another interesting point is they are only running 285cc injectors,  im using 540's at 60%  =  324cc worth fuel.  guessing they could be running high fuel pressure otherwise would be 100% duty for that power

Looks pretty good vs this one considering down 200cc

22569506_151kwvsmotoiq.jpg.6b59420a24896944b2292de5604eda68.jpg

 

 

 

 

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That’s interesting. Here is the dyno sheet for the 20v. Is flywheel kw the tuner works on a 16kw drivetrain loss for this car. Hopefully the data is useful. 

The best engine we had was about 12.5:1. over that it’s diminishing returns over that. Below graph is 13.5:1 but hasn’t really run reliably with that setup. 

Also found header design for reference  

99BDE013-FD8D-468C-BE4A-2E77CF2F5FC7.jpeg

0CAB3412-8946-44DA-A1D7-5506B9A13361.png

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Interesting data from this book I’m reading that might help explain the tube diameter change (or lack thereof);

engines typically produce peak torque at a mean gas velocity of 250ft/sec. (peak torque rpm is determined by size of pipe diameter) 

the max hp of the engine is determined by the pipe diameter 

changing the length of the pipe tends to ‘rock’ the power curve of the engine around the point of maximum torque

 

Here’s some interesting data about primary tube diameter;

933AAED5-6CF1-460E-A535-CE7292019396.jpeg.031f443f3a997f719ba811b17fea3118.jpeg

Stepped headers; 

094DFCCD-DEF0-4553-B026-E672B4565496.jpeg.ee949f1af719862bda26bac25cc338e6.jpeg

and data on venturi collectors;

25B24B59-9936-44D5-BE0C-0E5A01304366.jpeg.67897972f56d6d1d5d9f14d345aef1eb.jpeg

 

 

apologies for the spam in your discussion thread! This subject has got my brain ticking over far too fast in the last few days..

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all good its not spam,  pretty interesting, always looking for new ideas to try.  will have a better read though those pages later.

 

heres that chart overlayed.  i started  the overlay at 30kw at 3000rpm same as flywheel power, as assume wouldn't  be loosing 16kw  down there..
looks about right since smallports naturally spit out more  midrange than the other 4age versions

1363918169_151kwvsrhyscar.jpg.944540e62f6f6da9fb4bf7aaa64ecca3.jpg

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while we are on the subject,  remember that time at meremere a NA 16v  beat a turbo 20v.   @Stu

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