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Posts posted by kpr
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hmm yeh pretty sure you'll be still in the hole at that length. I'd try another 50mm longer. taper along the whole runner, thats a little less aggressive than whats in those throttle bodies. bendy ones like you had before will be fine. long as long radius. maybe can use the radius of the bend to fit the injectors on top side with less angle. either way will be worth trying longer with/without the outboards.
something like so,
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I've asked you a million times. but what is your runner length to head, and guesstimate to the back of the valve? as you say maybe long enough already. or in the no mans land before getting another "peak"
Maybe try similar to what you have, but put a taper across the whole trumpet. a few degrees included angle is good. seems to be a tiny bit in it.
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Its pretty silly how far can oversize the inlet runners with only small negative effects at low/mid rpm. Which makes sense for the majority of the 80's/90's "performance" heads with massive port entries and runners. easy just to overkill it and take a small hit low down. going too small on the runner you can actually see engine hit a brick wall and flat line. with only a small benefit down low. unfortunately there doesn't seem to be any sweet spot that will get you a significant gain down low without restricting top end. If make the runner small enough to gain anything significant low down, it will loose top end.
Not saying there isn't something in getting the diameter right. but far less sensitive that you would think if err on the big side.
also, there are plenty of people out there that will show you big gains down low/mid from a small diameter runner. which is usually a band-aid fix for sucky exhaust side. as your increasing intake pressure to overcome a reversion issue. they will have lost top end power doing so.
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Think I will do a little bit of a revisit on intake runner lengths, now my engine has vvti. I think the length I was using with fixed timing will be at least still very close to where it needs to be. Tuning the intake to where engine where it wants to make peak power. Then using the vvti extend the peak power both ways
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Calculators have there place getting you ballpark. or if have no idea on starting point. can cut down on testing time, if that's the case. Or at least a good learning exercise. As a lot of people still seem to go with a blanket "shorter is better for high rpm, long is better for low rpm" Yes if make the runner shorter it will push the tuning higher in rpm range. The part they miss is, if make the runner longer and drag one of those previously unreachable peaks down to where the engine naturally wants to make peak power. you have just had a big win. as said peak you have pulled down, is stronger than if you shortened the runner, to push a peak up the rev range. Plus you get the benefit or pushing all those other peaks down the rpm range and gaining midrange power as well.
you can see this in my videos pretty clearly. if the runner is too short and the peak falls off the end of the rpm range. it chops the top off the power curve. So yeah im actually using the longer runner to make more peak power which melts most peoples brainsThere are of course other things to overcome than just length. but yeh, gets you most of the way there.
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This ^
Pick up that jumbled up box of lego. do some illegal moves according to internet theory, and lots of testing- 2
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Not much to add since @Roman has it covered, Although a graph would be nice? The few bendy runners ive used. the centerline measurement seems to line up pretty well with a straight runner. in regards to length tuning
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Re driveshaft, easy way to think if it. is the shaft is going to be spinning the same rpm as engine in 1:1 gear. (usually 4th) Then punch the numbers into that calculator @cletus posted.
Single piece becomes a bad day fast, on a high rev engine that will be generally matched with short diff ratio. if going to use it on the track etc
I usually avoid running anything up on dyno in 4th gear with a single piece that's going to pull some revs
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Possibly. On stock stuff you kinda have to think about what the manufacturer is doing also. since their game isn't just what makes max power everywhere.
This is what it does on my turbo junk. if just want to look at graphs. 8:18 for exhaust and 5:54 intake
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Looks faster at least
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Yeah its doing pretty good for what it is.
blue line is my "good engine" with fixed timing. Can see where im heading with this..@mjrstar Yeah can see how it would be more benefit in some situations that others. My turbo engine seems to like the same numbers as an na engine. both with stock cams. but in saying that its only running low boost on a turbo that has plenty more in it. so pressure ratio will be pretty good.
On my na setup, the exhaust cam is usually pretty happy to stay where it is, even after some fairly aggressive changes to inlet. Will be a little bit in it. but not enough to bother going dual vvti. coming from someone happy to scrape up a few kw here and there.
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I probably (most likely) done a shit job of explaining what i meant. The exhaust valve is long shut before the compression stroke starts. so doesn't matter when the air fills the the cylinder on the intake stroke. long as the amount is the same. it will squish it the same amount on compression stroke and make the same power. so lower dynamic compression just means you lost cylinder fill / power?
Guess its just the fact the intake valve is open to intake manifold after bdc that its acting like a smaller cylinder when air speed low.
/1nzfxe
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@mjrstar Is all about the intake cam. I never really got how everyone says need to run more compression to compensate for big cams. seems like something from the past, when installing bigger cams engine has to lose bottom end power. so add more compression to compensate, plus can get away with more compression since it doesn't make power till higher in the rpm range.
But if do things right you can jam at least as much air in over the whole rev range. even without vvti
@Dudley only 1/2 race bro, cant go full hectic all at once
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More graphs and loud noises , shows better how big the shift in cam timing is
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You'll loose bottom end using big cams and modifying your NA engine. Ok i'll take the hit at 1700rpm
The vvti works amazing on the bigger cams, nothing like the weak gains on the stock cams.
Some fixed timing compromises:
Light Pink (salmon?) 25 deg- pretty much matches the peak power. but massive hit in midrange
Green 30 deg - kinda blah. may as well run 25 as above ^
Pink 40 deg - probably good compromise for midrange while not loosing a whole heap of peak. good if didn't want to rev past 8500.
Bright green vvti - all the power everywhere. actually using way more range that i thought i would need, about 45 degrees. I didn't spend very long at all on the vvti map. so some tweaks may get another kw here and there. and yes it made 138kw!
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doing a massive burnout to get the oil temps up helps!
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Yea as above engine spins in same direction so cams do as well.
Basics of it is, there is a advance camber and retard camber. to advance cam, solenoid sends oil down advance gallery. at the same time it opens drain on the retard gallery. same shit but the other way around to retard the cam. to hold the cam at a timing number will be equal pressure on both sides,G oil feed
D cam advance
E cam retard
F drainThe 20v setup i had on there just has one oil feed to pulley to advance cam. and relies on rotation of engine to retard the cam back to zero. no need for cam shaft position feed back, since its just on/off
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Everything is custom made or modified parts off various engines. I spent a lot of hours machining stuff. but even more figuring out how to make everything fit and work. so yeah nothing really bolted on, but was interesting how some stuff off other engines fitted together with some butchery.
I may have got away without doing it. but i used the bigger jz pulleys to allow more room to get the oil feeds to the vvti. also liked the idea of going to a wider belt and higher pulley tooth count at same time.
went for the jz pulley over the beams, as heard stories they are a complete dick put back together if pull them apart, due to having a big spring in them. the jz one is a walk in the park to pull apart put back together. Its also cheaper to buy new
Theres only a tiny advantage having it on the exhaust side power wise, not worth the effort
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So I pulled the head off looking for bendy valves in cylinder no3. but all looked good. guess kinda makes sense the rings are toast in that cylinder will all the smoke. the whole thing was built with worn out old junk and all the bores look horrible. but need to test more stuff. so put it back together with a trd head gasket. that had been reused, i lost count how many times. stock 1.2mm trd .8mm metal. some copper coat and back together again
Still smokes like a train as expected. try not to let it idle so doesn't fill the cylinder with unburnt fuel..
seems to have gained about 3kw. 2kw at worst with the trd head gasket
100c run same as above, 120kw on stock cams!
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Ok, so i ignored all the oil leaks and bent valves, put it on the dyno. most of its working as planned.
im not sure how fast its meant to respond. this is unloaded 1st,2nd,3rd and bit of 4th on dyno. which is a bit faster than it would accelerate on the road. It doesn't keep up in 1st, which is borderline free revving. but the rest is pretty good. some adjustments probably can get it even better.
first attempt I had it setup for too much advance and not enough retard. so skipped a tooth on cam belt which got it pretty close. after a few runs with cam timing fixed at different settings, built a rough vvti map.
using around 35 degrees of travel throughout the rev range. It could go a few more adjustments, as can see in the graph below where the fixed timing slightly edges it out in places.Doesn't look super impressive, but weak stock cams will do that
Red is vvti holding 28degrees throughout rev range, which simulates the best compromise on a fixed timing setup
blue is my rough vvti mapTo get that 114kw peak on a fixed timing setup would lose a huge amount of midrange
After that i had a play with the exhaust cam timing, was slightly off. then run it up at 100deg oil temps. i usually run tests at 90 or 95 because easier to keep there. but hotter oil will make more power
Almost 117kw with stock cams (not even bluetops) and some bent valves and an amazing amount of smoke coming out the exhaust. must be some kinda record?
red is stock ish bigport. same good header and exhaust. stock intake. same cams!- 24
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Got a bunch of teething issues and stuff to finish properly. but managed to run it for a bit. it was a bit wacky on the "2jz" vvti settings. after messing around with the pid settings a little, looks promising. cam is advancing and retarding and matching the target in vvt map.
The cam belt and pulley setup works good, no issues. have a 25mm wide belt on there, stock is 19mm.
Also this engine is stuffed, I had incident where the bolts backed out (may not have tightened them properly) of the 20v vvt setup. the inlet cam jammed up and bad stuff happened. after that it was down 5kw or so, but still made over 130kw ha! compression test come back 150, 150, 100, 150. now with stock cams back in it its super obvious, runs on 3 cylinders until get over 2000rpm.
I'll pull it apart once happy with how the vvti setup works.
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spinning triangles with magnets
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Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt
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If hard up it for that long, would be pretty normal. would suggest getting it checked if unsure on the tune though