na cams in vr4

[billybobboot]

Ive done this swap with other cars with good results mostly on toyotas my question
1. Will na cams fit a vr4
2. Car the cams diffrent i know normaly na cams are slightly more aggressive than turbo cars.
3. If they fit will inlet cams fit the exhaust side again had good experience and gains from toyotas but taking the last 3sge cams putting in early 3sgte running both exhaust and inlet with inlet cams and made a big diffrence but that was 345 bhp+ car

[Nick Mann]

Someone will be along with more knowledge than me soon, I'm sure, but my understanding is that the exhaust and inlet cams are the same. However, the na is sohc and the turbo is dohc so I doubt that the na cams are useful.

[SEAN-NZ]

Wont work, considering intake and exhaust are on the same cam, as nick said, na is sohc, turbo is dohc, maybe if you ground off half the lobes, depending on position, but I wouldn't half a clue if that would work

[hbkuk1]

You can use 6a12 cams from an fto gr there better than stock vr4 cams and a direct fitment. The 6a12 is exactly the same as the 6a13tt in almost every way

[Davezj]

any info on the specs for the 6A12 cams.

[Adam.Findlay]

If someone can get me some stock 6A12 NA cams I can measure them and tell the difference. But I can tell you now it wont be bugger all difference if there is even a difference at all.

[Davezj]

didn't you use some Mivec heads from a 6A12 in your build adam. but I suppose they would have been from a turbo car for the compression ratio.

[Nick Mann]

I'd imagine mivec heads have a different cam setup. I believe mivec is a kind of variable valve timing, so cam trickery must be used somehow. My guess is Rich has used some non-mivec 6A12 cams.

[hbkuk1]

Mivec cams won't work with our engines

[foxdie]

Mivec cams won't work with our engines

Could you cite this?

[foxdie]

Admittedly, the mechanics behind cams, lifters, etc baffle me, but if mechanically MIVEC heads from a 6A12 will fit AND work on a 6A13TT, and the only problem is controlling them, I'm quite confident that Kenneth could adjust his KS 2.0 ROM code to toggle one of the +12V pins depending on which profile was activated (this would be configured in the bitfield section). That pin could then toggle a relay to control an actuator to select the timing profile.

Finding a pin (http://www.clubvr4.com/forum/showthread.php?59222-Definitive-EFI-ECU-Pinout-(KS-Mod-friendly)) may be fun though, I'm thinking one of the following could happen;

* Pins B1 & B2 control valves that reportedly aren't present on facelifts, maybe one of these could be used, and in the case of a pre-facelift, the recircs left open / closed?
* Pin B5 toggles the fuel pump high / low speed relay, this could easily be re-purposed if the fuel pump was hot-wired (chances are if you're going for big power this'll happen anyway)
* There are numerous other unconnected pins that may have traces on the PCB, these would require further investigation (I may have to get out the magnifying glass again)

My thinking is this;

1st profile matches engine speed above 4500 rpm = aggressive cam profile
2nd profile matches engine speed rpm above 3000 rpm and throttle above 80% = aggressive cam profile
3rd profile matches everything else = normal cam profile

Granted this is all theory, but whilst we're still in the realm of the uncharted, I wouldn't at all be surprised if there were some good power / torque gains to be had here, I'd be happy if we saw breaking the 350 HP mark with stock turbos without meth / N20 :) (but again, that's speculation)

Naturally, Kenneth will need compensating for this (bounty perhaps? That or shedloads of alcohol :D).

[hbkuk1]

Ok let me modify that what I mean is they will work but not without changing the heads as the mounts are different the valves and crowns are smaller on these heads which would negate there usefulness AND then you would need to control it. What I should have said is they won't just bolt in like non mivec ones will with no other problems

[foxdie]

Ok let me modify that what I mean is they will work but not without changing the heads as the mounts are different the valves and crowns are smaller on these heads which would negate there usefulness AND then you would need to control it. What I should have said is they won't just bolt in like non mivec ones will with no other problems

Right, right. Shame that.

[Davezj]

did the 6A12 engine come with Mivec heads and without Mivec heads. for some reason i thought all the 6A12 cam with mivec heads. but maybe to was only the later ones to imporve emissions.

i was sure it was Adam.Findlay that had put mivec heads on his 6A13. but i could be wrong.
the Mivec heads are the ones that split into two parts when the cams get removed aren't they.

ok so here is a question for you, do the mivec cam pulleys fit onto the mivec camshafts in the same way as the standard cam pulley fit on the standard camshafts.
which begs the question if the NA 6a12 camshafts were a more agressive spec, mivec or not would the standard pulley fit these camshafts and would these camshafts fit the 6A13tt heads.

i obviously don't know the answer to these question which is why i am asking them.
this is just interest form me, i am not planning anything.

[Adam.Findlay]

this thread has wildly derailed into a MiVEC (Mitsubishi innovative Valve Electronic Control) conversion conversation which is covered elsewhere in my build thread but anyway

Mivec in the 6A12's is not Variable Valve Timing like Toyota's VVTi or Nissans NVCS, it has two separate cam profiles and when MiVEC engages it simply switches from the small cam profile to the large cam profile much the same as Hondas VTEC
I am using mivec heads for my build yes but the mivec heads are completly different to normal DOHC 6A13 or 6A12 heads they are not a bolt on affair, you need to fabricate an intake plenum to suit as the ports are different size and shape and the bolts for the lower half of the runners are all wrong for a stock intake to bolt on, some trickery needs to be done with the camblet idlers to get the cambelt to fit and because of this you need adjustable cam pulleys to get the cam phasing correct. and due to the smaller combustion chamber volume the compression would be much higher on a 2.5 block using these heads and as Foxdie said you need some way of driving the Mivec solenoids to actually engage it, either by configuring an unused pin on the std ECU via KS mods or using a full aftermarket wire in ECU like I have.

The mivec cams are completly different and DO NOT fit in regular 6A12/13 heads, although yes the high speed lobe (the one engaged when mivec is active) is quite big, 300 degrees in duration to be exact. The cam pulleys from a 6A13TT will bolt onto Mivec cams but the cams wont fit into the heads so that information is pretty much useless.

Anyway back to something relevent..
the N/A 6A13's are SOHC so that clearly doesn't work in a DOHC head.
6A12TT cams are smaller in duration and lift compared to 6A13TT cams. however these cams are interchangeable, as are the NA 6A12 DOHC cams

Its a common thing for manufacturers to put bigger cam profiles on naturaly aspirated engines, Nissans SR20, RB20/25 are both good examples of this, I would not be surprised if the 6A12 N/A cams are bigger than the 6A12TT cams but I am unsure if the 6A12 N/A cams are any bigger than the 6A13TT cams. hence why If someone can loan me a set (or even just one intake and one exhaust) of 6A12 DOHC non mivec cams I can use the special cam doctor equipment at work to accurately measure and compare the lobes.

Also as most of you know I offer the 262 degree 9.8mm lift regrind on the stock cams, If it turns out that the 6A12 N/A cams are bigger than the 6A13TT cams I may be able put an even bigger grind on them again something closer to 270 and over 10mm. I don't know yet though would have to measure some to find out. Any Questions about cam stuff fell free to ask as camshafts is what I do for a living.

[Davezj]

Excellent response Adam, that covers all the question and more.
And delivered in a way even I can understand. Should prove very useful to refer back to in the future.

Thanks

[Downundersir]

Any progress with getting a set of cams sent to Adam ( +1 great response) for measurements?

[Adam.Findlay]

Not yet.. surely someone has to have some lying around

[hbkuk1]

I have a spare fto 6a12 no mivec engine if I get the chance I,lol whip the cams out and you can take a squiz as I would like bigger cams than the 272s I already have

[Adam.Findlay]

Wont be able to regrind stick cams that big but I make new billet cams. PM me for details

[billybobboot]

Ok so we any closer to knowing if its worth doing this? If not ill just get a set of cams as if i got to do a belt i might as well do the cams now along with lifters.
Only reason i didnt do it was belt was only a year old with 5k on

[Adam.Findlay]

Noone has bought me 6a12 NA cams to measure yet but even the 262 regrinds is well worth it. Goku picked up 50hp at the wheels with a set of reground cams.

[billybobboot]

Yer thats what im thinking of doing.

[giblet]

Noone has bought me 6a12 NA cams to measure yet but even the 262 regrinds is well worth it. Goku picked up 50hp at the wheels with a set of reground cams.

Are there any auto cars that are running your cams. I'm interested to know what sort of power I could get from my car with a budget of around £1000.

Obviously it will depend on mapping etc but at the moment it has fmic, colder plugs, downpipes and decat amongst other things plus Kenneth's map. Would reground cams, 3 port solenoid and a proper remap see me close to 300 atw?

[billybobboot]

Youll need fueling mods too my stock pump was maxed at just under 300 at fly i would expect to see around 260-280 at wheels all comes down to engine, mappers, supporting mods ect i have know same parts on 1 car get more with same parts on another car. On stock fuel i would expect to be close to the limit of everything at 300 at wheels. As far as injectors and turbos go.

[giblet]

Uprated pump waiting to be fitted. I'm on LPG which is why I've not had it fitted yet. Not had time to fit my hardpipes yet either.

[billybobboot]

Ah you should hit 300 then. Im on pump gas as i have no room for lpg sort of want it but not at same time but i dont really care about fuel costs.

[giblet]

You don't care about fuel costs? My fuel savings have already exceeded the cost of conversion and it's only been a year since I had it done.

[billybobboot]

Not really i drive a powerful car im not expecting to get fuel economy, my car history is celica gt4s mr2 rx7s and the legnum. I dont need a car to get to work. Ive spent 700 on fuel for a week holiday before. Not saying lpg isnt a good thing i just not sold on it due to having the system on the car. I realise i would save a silly amount on fuel but as i said if i want fuel economy ill take the wifes car.

[giblet]

I'm on my third VR4, also owned a few other thirsty motors including a 4.0 supercharged V8 Jag. The money I save on fuel is put towards upgrades etc. For me it's a no brainer at 15p per mile vs 30p per mile. Only downsides are how long it takes to fill up and not having space for a spare wheel.

[Grid]

I'm on my third VR4, also owned a few other thirsty motors including a 4.0 supercharged V8 Jag. The money I save on fuel is put towards upgrades etc. For me it's a no brainer at 15p per mile vs 30p per mile. Only downsides are how long it takes to fill up and not having space for a spare wheel.

Not to mention the added 200 pounds of weight further reducing the handling and straining the brakes. All depends on what you are planning to do with the car. IMO if it's a daily family car why not. I kept my V6 N/A Galant for fuel economy reasons, and the Legnum I drive to work, for fun and on trackdays.

[giblet]

Not to mention the added 200 pounds of weight further reducing the handling and straining the brakes. All depends on what you are planning to do with the car. IMO if it's a daily family car why not. I kept my V6 N/A Galant for fuel economy reasons, and the Legnum I drive to work, for fun and on trackdays.

Not sure on the exact weight but 200lb seems a tad high. Even so, can you honestly say you can tell the difference in handling and braking on regular daily driving with the weight of an extra passenger? This is a performance car we are on about, not a stripped out track special.

[billybobboot]

Yes you can tell the diffrence i have radio stuff in my car removed its far lighter at the back and dosnt feel as tail happy with the weight out. But i take it out if i know im going driving to go driving.