Need input from those with a FMS cam

[blkfordsedan]

I need some input from those running a FMS comp (street) cam.
Preferrably, if your running it on a B6 with a ported head....but even if you have a stock B3 w/FMS cam it would be helpful.

I'm curious as to what RPM the camshaft starts to pull and where the peak torque is at. I'm trying to decide if I want to just install my cam with the stock sprocket or if I want to spend the time to try to re-machine the sprocket so that I can advance the cam about 4 degrees.

Any input would be appreciated!:p

[getnpsi]

I've read that all mazda b-series cam gears are the same, so you can get some miata gears off the net used for cheap. Then build 2 engines!

[blkfordsedan]

Never thought about buying a used set of gears, that's certainly a viable solution.
But, I still want to get an idea of the the RPM range of the FMS cam and how it performs. I'd like to be in the torque curve by 2500 if possible. That would be ideal for all the highway driving I do.

[FestYboy]

youll have to advance the cam 2-3* for it to come in that low. Scrappy doesn't start pulling till after 3k. (B6, ported)

[gauge_half_inch]

I have the FMS street cam with a 92 b6 with mild port work, at 2900-3000 you can feel the power kick in pretty hard and it pulls even harder after 4000 thru rev-limiter at 6400. It does help at about 2600 as they Stated in their description. The only down side, is fuel mileage suffers pretty drastically.

[ToSloTrk]

Installed a FMS cam in a B3 w/ported and milled head.
Ran it straight up and advanced.
Straight up was by far my favorite as advanced it gained very little on the bottom and lost plenty on top.

[blkfordsedan]

youll have to advance the cam 2-3* for it to come in that low. Scrappy doesn't start pulling till after 3k. (B6, ported)

I have the FMS street cam with a 92 b6 with mild port work, at 2900-3000 you can feel the power kick in pretty hard and it pulls even harder after 4000 thru rev-limiter at 6400. It does help at about 2600 as they Stated in their description. The only down side, is fuel mileage suffers pretty drastically.

So, I guess my questions are; how is the low end as compared to a stock motor, or even a B3? I assume that even with the FMS cam, the idle-3000 RPM range is still stronger? Based on what you guys have now, do you think it would be better to advance it, or is it livable as is? Does the 3000+ RPM range make it pudgey down low or awkward to drive in a normal manner or at a 60-65mph cruise? What would you do if you could do it again and had the chance to advance it?

[blkfordsedan]

Installed a FMS cam in a B3 w/ported and milled head.
Ran it straight up and advanced.
Straight up was by far my favorite as advanced it gained very little on the bottom and lost plenty on top.

Thanks for the input! Your findings are really making me think twice...Can you expand on it a little more? How many degrees advanced did you set it and how did you do it? Do you have a stock B3 exhaust manifold and exhaust or a tube header?

I'm guessing a B3 probably responds a little different than a B6. The smaller bore diameter, valves, ports and the longer rod ratio will have different characteristics in terms of cylinder filling.

[fastivaca]

I have the FMS street cam with a 92 b6 with mild port work, at 2900-3000 you can feel the power kick in pretty hard and it pulls even harder after 4000 thru rev-limiter at 6400. It does help at about 2600 as they Stated in their description. The only down side, is fuel mileage suffers pretty drastically.

I'm running an early B6 with similar mods to the head and my experience is very much the same as far as power and pull etc. I haven't experienced any major difference in fuel consumption though. When I went from stock B3 to stock B6 my gas mileage dropped about 5% and then when I installed the ported head with FMS cam is dropped another 5%. I think a portion of the drop could be attributed to increased use of the gas pedal in order to enjoy the added power. All in all I'm happy with the improved performance. On our big road trip to Raleigh and back, over 6000 miles, we averaged just over 36 piler per US gallon with five of us in the car, A/C running about half of the trip and mostly at interstate speeds.

[ToSloTrk]

Thanks for the input! Your findings are really making me think twice...Can you expand on it a little more? How many degrees advanced did you set it and how did you do it? Do you have a stock B3 exhaust manifold and exhaust or a tube header?

I advanced the cam approx 4 deg by grinding the hole in the cam gear a bit.

one tooth on the cam gear = 7 deg.

stock B3 manifold with 1 3/4" exhaust w/ glasspack

I've also installed an FMS cam in my B6 and didn't have nearly as great results (need to yank the head and port it)

[blkfordsedan]

^^^^That's the thing. When we talk about advancing the cam 4*, that's in reference to crankshaft degrees. Like you said, one tooth on a 46 tooth cam gear is approx. 7.83 camshaft degrees (360 / 46). Since the crankshaft sprocket is half as big, one tooth of angular rotation on the cam sprocket is worth 2X or 15.66* at the crank. In order to get 4* rotation on the crankshaft, I need to change the cam sprocket by 2*............which is just a hair over 1/4 tooth. That's a very small amount (about 2mm or .079") at the pitch diameter of the sprocket. If you project that distance down the angle to the location of the cam drive pin, that amount now becomes only about .007".

I'm not quite sure how to accomplish that. Seems you would need to drill the drive pin hole in the sprocket oversized and use a precisely machined offset bushing. That's how a lot of the aftermarket cam degreeing kits used to do it. Since advancing the cam means moving it in the same direction of rotation, simply enlarging the hole on the non-driving side would do no good since the pull of the belt would only cause it to revert back to the stock location. The only other means would be to treat it like a multi-indexed crank sprocket and drill a completely new sprocket drive pin hole somewhere else around the center. Then you just have to make sure to place the hole centerline so it lines up approx. 1/4 tooth farther ahead than the original hole was in relationship to the closest tooth. I haven't quite figured out how I'm gonna do this accurately yet, LOL. If you have any details on how you did it let me know!

[ToSloTrk]

Made a base mark on the head and used my dremel to grind the drive pin hole untill I got the advance I wanted.

I just torqued cam gear and didn't have any problem with it slipping back to original position.Defenitly not a professional way to do it but it worked for me.

I understood advancing a cam is camshaft deg. but I've been wrong before.

[blkfordsedan]

Excellent....thanks!

Hey, if it works, it works....no criticism of your method here! There's no substitute for actual experience, that's why I asked.

[gauge_half_inch]

I'm running an early B6 with similar mods to the head and my experience is very much the same as far as power and pull etc. I haven't experienced any major difference in fuel consumption though. When I went from stock B3 to stock B6 my gas mileage dropped about 5% and then when I installed the ported head with FMS cam is dropped another 5%. I think a portion of the drop could be attributed to increased use of the gas pedal in order to enjoy the added power. All in all I'm happy with the improved performance. On our big road trip to Raleigh and back, over 6000 miles, we averaged just over 36 piler per US gallon with five of us in the car, A/C running about half of the trip and mostly at interstate speeds.

Part of my mileage is the 205/50/15s I'm running.

[blkfordsedan]

[QUOTE=blkfordsedan;465498] If you project that distance down the angle to the location of the cam drive pin, that amount now becomes only about .007".
(/QUOTE]


My bad. Actually it would be .014" at the drive pin. Still a very small amount.