Need info on cams ....

[nightspeed87]

I am in the process of a 6bolt swap and rebuild, and the guy building my engine asked if I want to run n/t cams, because supposably they have longer duration and a different power band than the turbo cams... I have also heard that the cams from the 93 turbo eclipse were more aggressive than the other yrs, and that the 90s yr were the most mildest... The 6bolt engine going in my car is a 90s engine... The machining shop already built me a new head with new valves, lifters , shaved etc. but im opting for the cam decision now... I have some n/t cams I could use from my old n/t.... What should I do... Is there any turbo guys running n/t cams, or is this completely a undesireable and bad idea????
Does anyone know the differences of the powerband between the two camshafts? And is there any downfall to either....


(( I want most of my powerband to be like between 4k to redline, I dont need too much low end hp Eventually I will get some hks 264/272 camshafts or something of that nature but that will be way later down the line... )

 

[GVR4592]

I'm willing to bet you're one of those guys that finds out the toilet paper is missing right when it's time to wipe.

http://www.dsmtuners.com/forums/showthread.php?t=17110

I always check before I squat.

 

[nightspeed87]

i didnt need the smart ass remark, for some reason maybe its my computer or maybe its the website but it keeps kicking me out every time i clink on another link, and I cant stay logged in long enough for keep my computer from going tooo slow to even look anything up so i had to just type it... This link you supplied was helpful despite that half of that was way to technical and went over my head, but did supply me with some info, but still doesnt flat out tell me to either use the n/t 1g cams or not...

I just want to know benefits/ downfalls to useing the stock 1g n/t cams over using the turbo cams.... If no one knos then ill will try a search later at a different computer. thanks anyways.

 

[GVR4592]

If you read it again, it clearly says which cams will give you the most power

Since we know that all year's cams were ground on the same base circle
one can conclude that there was at least some changes in maxinum lift, based on this data. One could conclude that the most desirable choice would be an intake cam from a manual trans car, and a exhaust cam from a 93 and later turbo manual car.

 

[nightspeed87]

According to the service manuals I have the 90-92 4g63s all had the same cams. 1993 and later cars were as follows.

90-92
intake 1.3974 lobe height
exhaust 1.3777

Intake cams
NT & Turbo w/manual trans 1.3974 lobe height
Turbo w/ auto trans 1.3858

Exhaust cams
NT & turbo with auto trans 1.3858 lobe height
Turbo with manual trans 1.3974

Since we know that all year's cams were ground on the same base circle
one can conclude that there was at least some changes in maxinum lift, based on this data. One could conclude that the most desirable choice would be an intake cam from a manual trans car, and a exhaust cam from a 93 and later turbo manual car. This is interesting since mitsubishi listed a BHP change in the turbo cars between 92 and 93 of 190 to 195 respectivly.

ok i gather that n/t and turbo intake cams are the same...
And I understand that the 93 exhaust cams have better lift on a turbo car
but where it says an intake cam from a manual trans car ( there not being too specific... )
and it doesnt say what the n/t exhaust cam is, but obviously then that means just get the turbo 93 exhaust cam,...
But then this part throws me off, because the values are different here and i want to know what this means-

Maybe I don't know what I'm doing but it seems that you can calculate the overlap by simply looking at when the intake opens and when the exhaust closes.

Based on what I can tell from the service manual the 1G 2.0L cams differ as follows: (specifications pages, timing is in one place, lobe height in another)

Intake NT opens 26 BTDC close 46 ABDC lobe height 35.493 (34.993 limit)
Intake MT opens 21 BTDC close 51 ABDC lobe height 35.493 (34.993 limit)
Intake AT opens 21 BTDC close 51 ABDC lobe height 35.200 (34.700 limit)

Exhaust NT opens 55 BBDC close ATDC 9 lobe height 35.200 (34.700 limit)
Exhaust AT opens 55 BBDC close ATDC 9 lobe height 35.200 (34.700 limit)
Exhaust MT opens 55 BBDC close ATDC 9 lobe height 35.493 (34.993 limit)

From this I come up with the NT intake cam being 252 duration, the turbo intake at 257 and a duration of 244 for the exhaust. NT has 35 degrees overlap (26BTDC + 9ATDC) and turbos have 30 (21+9). These are seat timings. From the point where the valve first starts to move.

Is my math correct?

What does he mean here when it says n/t has 35 degrees overlap, and turbos have 30...
Is overlap good or bad? and it says n/t duration 252 and turbo duration 257 on the intake cam, so would the 257 just means the power band comes in higher right, and the n/ts 252 would come in sooner??? Dont you want the intake to come in sooner and exhaust to stay longer(higher i mean) for a broader power band?
and depending the exhaust cam is when the power would start to fall off????

the NT has 35 degrees overlap...everything else looked right. if you increase the overlap to 33 how luch will you suffer from reversion. the main reason they try to limit the overlap is so the high turbo backpressure does not blow the intake charge back up the intake.....then again if your going all out, want top end and have a really well flowing manifold and turbo this would be a good move...btw, thanks for the cam numbers and math.

Also this ^ makes me think that im right, and that the n/t pulls in sooner on the intake side therefore up here he may be suggesting that it wouldnt be good from all the back pressure the turbo makes to advance it like this?? ( Im still guessing remmeber) but maybe would be a good move with a really free flowing engine..
( I dont know if 3in dp and exhaust all the way back, ported 14b, and o2 housing is freeflowing enough? )
( Im sorry im trying here, I have to learn this some how, this cam stuff is a little complicating. ) Any wisemen can pitch in and help me out.