Jump to content

kpr's starlet


ratt

Recommended Posts

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

 

 

  • Like 4
  • Thanks 2
Link to comment
Share on other sites

  • Replies 635
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

I have spent approximately zero time trying to understand vvt inner workings besides needing oil pressure but one thing that strikes me is isnt the JZ intake on other side, i never really thought about it but i presume they spin the other way. Did that matter when setting up the vvt for advance/retard or is the valve pretty happy acting in either direction?

Not sure if viable but potentially a market in RFB world, RB26's (and early RB20s at least) dont have VVT and the 'only' off the shelf solution appears to be using the HKS v-cam. I have read one or two retrofit suggestions but not seen anything quite like this for 16v 4age that you've achieved

Link to comment
Share on other sites

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  drain

 

JZ_valve.png

The 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

 

 

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

keen to see how you hooked the oil up and machined something to hold the solenoid valve, iirc from the beams 3s's i used to play with they just got their oil supply from, and were just slid into and and bolted to the head - again never thought about it too hard besides replacing when i broke the poor plug, in stock guise is oil to the valve from its own line/gallery?

Link to comment
Share on other sites

I'm feeding it off the main oil gallery front of engine.   

The solenoid part is the easy bit.   Just have it remote mounted.  A v2 maybe on the cards to try eliminate some of the lines . 

20220328_204448.thumb.jpg.ffe356186bf07e15a301bb6c7e990eb6.jpg

  • Like 2
  • Thanks 2
Link to comment
Share on other sites

  • 2 weeks later...

I think I have mentioned this before but being able to swing the camshafts is a game changer, on a twin cam with both cams swinging there is almost no downside to going for what would otherwise be considered quite a large camshaft (well other than piston to valve clearance of course) 

What I hadn't seen before is just how successful swinging one cam is, I had thought (maybe wrongly) it would impact compression.. 

Great work! 

 

Maybe up next is get Roman Dave to do a compression test graph whilst you swing the cam? 

Link to comment
Share on other sites

@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

 

 

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

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

 

  • Like 3
Link to comment
Share on other sites

For sure big cam is a caveman problem and is really is about single cam application where you can't optimise lobe separation, or on your case move it to suit airflow velocity.. 

I was more thinking about the improvement you get in compression with a larger intake cam, or dialing when it opens and there possibly being even more swing you can apply to the intake cam if you had the ability to swing the exhaust to further optimise lobe separation?

It might not be a thing that helps though. Just theorising here. 

 

EDIT: perhaps exhaust cam timing becomes more exciting when turbocharged and having to deal with exhaust manifold pressure? 

Link to comment
Share on other sites

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..

1611399792_turd284284vvtivgoodengine.thumb.png.132354ebb6591634d5ea93197d307bd6.png

  @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.

 

  • Like 3
Link to comment
Share on other sites

@kpr for sure there is probably only a percent or two in it on an NA versus real gains on the inlet which you have really proved! not a lot to be had on the exhaust side for the added complexity /headache.. 

I did read a bit about a stock evo 10, which didn't pick up much power, but delivered a fair wack more torque from a standard setup by modifying exhaust cam strategy. 

There is probably low range spool gains to be made depending on "things". 

Maybe more so on turbo 6's like bmw and coon (where dual vct setups seem more common) , perhaps you don't get the same pulse grouping gains you get from a 4 cylinder? 

 

 

Link to comment
Share on other sites

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

 

  • Like 2
Link to comment
Share on other sites

I'm a subscriber but hadn't seen that video before, that is cool just how much earlier you can get the boost in with the inlet change. 

Oem have all sorts of things to worry about, noise levels, emissions, fuel economy, making a sport button that actually changes stuff etc

Vvti should be able to help on these too. 

  • Like 2
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...