fms race cam and boost?

[bobbyspider]

gauge uses the fms stage 2 street cam on his b6 single cam turbo with verry good results i was wondering how you think the fms stage 3 race cam would react to boost. maybe a dumb question but i thought id put it out there anyway. i could always just take the street cam out of the b6 and drop it in the b3 when i boost and put the race cam in the n/a b6. thanks

[PhoenixSHO]

Whats not good about race cams and boost is overlap , when the intake and exhaust valves are open in the same time. I have no idea on what is your cam specs but More theres overlap , more its not good for boosted application.

[blkfordsedan]

I agree with SHO. There are specific grinds with valve timing tailored to turbo apps, but I suspect too much overlap (especially in a smaller B3) would kill the low RPM and turbo spool. Also, from what I suspect, there were several different cam profiles offered by FMS over the years. Kinda hard to tell what you actually have. The FMS street cam in my B6 has substantially more lift than stock and slightly more duration. It doesn't have a lot of overlap (probably same one Dennis has). I bet it would work well in a turbo app. I would call Matt and see what he used in his turbo B3 build and what he recommends.

[gergorian]

I know in Matt's turbo B3 he opened up the overlap and re degreed the cam by re drilling the dowel pin hole for the cam gear. How much for both I cannot remember.

[bobbyspider]

^ so your saying it could be made to work? i know the cam has alot of overlap so thats why i was bringing it up. i dont have the race cam yet but have a lead on one. i may just put it in the b6 and take the street cam out of it and throw it in the b3. upgrade both

[gergorian]

I meant that Matt decreased the overlap on his cam for his turbo. From what I have read though the FMS cam should be fine although it is not at all optimum.

[blkfordsedan]

You could advance the cam a few degrees with an adjustable sprocket or drilling a new drive pin hole...that would help build some dynamic compression, but I would seriously talk to Matt about having a custom grind made or see what he recommends. Anyone who can get 200+ HP from a B3 on mild boost knows what it likes.

[gergorian]

You could advance the cam a few degrees with an adjustable sprocket or drilling a new drive pin hole...that would help build some dynamic compression, but I would seriously talk to Matt about having a custom grind made or see what he recommends. Anyone who can get 200+ HP from a B3 on mild boost knows what it likes.

Yes, Matt re-drilled his cam to advance it. But, now seeing that the Miata cam gear fits on the Festiva ( The only issue is that the bolt hole on the Miata piece is just a hair larger that the Festiva bolt). Maybe Matt could make a whole new adj. cam gear for the Festy or design and machine a center that will fit the Festiva bolt and work with the Miata outer gear.... I don't know. Hell, maybe Matt is already planning an adjustable cam gear and we don't know. But, I have to call him Friday to send a final payment for my header and I will ask him if he can or is working on an adj cam gear.

[bobbyspider]

^ word to that ! I'll check on it but I thought someone figured that out about the adjustable cam great? Don't quote me I'll look around and see if I can find it.

[mattdickmeyer]

bobbyspider....The cam specs on any engine, but especially a turbo engine, need to be appropriate for the intended usage. At the level of power & boost that you will be at, anything from FMS would most likely work as any cam from them isn't even what I would call a "performance" cam. Years ago, before I even started developing cams for these engines, after weeks of trying, I finally got a hold of someone from FMS. The vibe I got from him was that he only knew what a cam was because he had seen pictures. Realizing that they had no involvement in the development of their products, I decided it would be worthwhile to see what I could do. Yes, in the beginning, I welded the dowel pin in the cam gear & re-drilled to provide advance. But, in grinding cams, any advance can be ground into the confines of the cam core making an adjustable cam gear unnecessary. The cam specs that I used on my turbo engine is 221/222 @ .050 .495 lift 112 LS. This cam was designed for a well prepared top end with a turbo or also as a good high performance NA cam with EFI. By the numbers, this cam would make a SBC chop. But as I said before, there is much more to a cam than the numbers. This is also a cam that is presently in the car in NA form & works perfectly. The only major problem I see with the cam that you are running is the tight LS with a stock head & turbo will cause, what is called, "passive EGR". Essentially your intake valve will open before the exhaust stroke is complete "an effect of overlap". When this happens on an engine with a low low cylinder head & a header with back pressure present (product of turbo charging) your intake charge will be contaminated with exhaust gas. This negative effect increases as boost level increases. Even tho FMS calls it a stage 3, you wo9uld think it would be aggressive, but it actually is not. The other problem is that I read many of you are running these cams with stock valve springs & that it is my understanding the FMS cam has .420-.450 lift, & I have found that OE springs bind between .390 & .450 meaning many of you may be running on borrowed time & this is something that should not be overlooked.

[gergorian]

^ thanks Matt for clearing that up!

[blkfordsedan]

I've wondered about the spring bind issue. Several members have been running the milder FMS street cam for years on stock springs without issue.....(Arty, Jim, Dennis...if I'm not mistaken). I guess the question is what is the actual lift on the various cams. From what it seems, the FMS "street" cams could all be different (whatever they could buy at the time). If I'm not mistaken, those guys are also running a B6, so maybe the springs are different (although I didn't think so). I never bothered to check for coil bind on mine, since no one ever reported any issues. The one time I talked to Roger at FMS, he couldn't tell me what the cam specs were, but he told me the "street" cam was safe with stock springs. Not a real assuring response, LOL. I plan on taking my valve cover off and checking everything out just to see what I really have at full lift. IIRC, my lift measured out at like .447".

[mattdickmeyer]

I am doing a bunch of work for a customer now who has done a SOHC B6 swap including a B6 specific cam & spring kit. The B3 & B6 valve springs measure the exact same ID & OD, just slightly different free length, but only by a few thousandths. Which I would attribute to the mileage on the engine, slightly collapsing the springs with age. Either way, my performance springs fit fine & provide sufficient bind clearance for .575 lift at OE installed height.

[mattdickmeyer]

I would never recommend the "install cam & hope for the best" method, tho I see it a lot. Some get lucky & some don't. I just checked a set of low mile Aspire springs for the heck of it. From installed height to coil bind occurred at .4375 lift. Keep in mind, this provides no bind clearance of .060 typical minimum. OE lift of .380 already maxes out the spring. You are probably squeaking by, by the skin of your teeth.

[blkfordsedan]

How much are your springs by themselves? If I got those first to run with my FMS cam for the time being...then I could upgrade to one of you custom grinds later on and not have to mess with it.

So, I suppose if I did have a very slight coil bind, would the HLA would probably bleed off, or would the cam lobe just force itself over center and create wear issues on the rocker pad and lobe?