I'm putting the T cam back in

[fivealive]

...cause this B cam is terrible... I took the B out of my '82 245 that got wrecked, and replaced the T. I adjusted all the valves properly too.

Of course, the car pulls a lot less vacuum than it did before, and fuel economy definitely took a pretty good hit. Main problem is though, the 1st gear acceleration totally sucks (no torque I guess).. I mean, I barely creep off of the line unless I rev the engine to about 4,000 rpms before I go.

I really loved the A cam that I put in my old 242, but I'm thinking that despite their similar specs, the B is just not a good turbo cam.

Anyone else have this experience?

[jpbturbo]

Are you absolutely positive that the cam is timed right?

I had a B cam in my car and it was only slightly less fun down low than the M cam.

[fivealive]

I'm pretty sure it's timed right, because when I get into boost, it pulls like hell. The car is just lacking a lot of low-end oomph.

[PetesDustyVolvo]

oops

[PetesDustyVolvo]

Originally Posted by adam_c

I'm pretty sure it's timed right, because when I get into boost, it pulls like hell. The car is just lacking a lot of low-end oomph.

That probably has a lot more to do with your 7.5:1 compression ratio, measly 2.1 liter engine, .63 A/R turbine housing and pistons shaped like crude caveman clubs [/johnv impersonation]

or perhaps its just that kjet sucks

[stealthfti]

The B only has ~7 thou more lift than an Acam does....and a LOT more overlap. The B doesn't come on until ~3000...if you have a decent flowing exhaust.

The overlap is not helping you out in a boosted context, nor does the later intake valve closing...which lowers the DCR a LOT more than does a T or an A. And with the lower SCR of a B21FT, you need all the DCR you can get.

Advancing a Bcam ~4 degrees might help with the DCR a bit, but doing that will still not do anything about the much greater amount of overlap.

So yeah, you're right: the B is not a good turbo cam, especially in a B21FT.

TF

[benflynn]

i was about to send off an A, but he might rather have a B...

[Canuckvolvo]

With a lumpier cam, you should be able to get away with more spark advance. Also, the kjet dizzies are curved to match the cam, so if you could get the distributor out of that donor car, throw the turbo vacuum diaphragm on there (for boost retard) that will help too.

[dl242gt]

You can do this or that. But even Volvo realized the B cam isn't as good for a turbo engine than the A cam. This is most likely why they went to the A cam when they introduced the B230ET instead of using the B that was in the prior B23ET. Try an A in there, advanced a few degrees if you want to use a Volvo cam.

[stealthfti]

Good point there, Athal. Although, if he's running an old style manifold/stock size exhaust, the overlap is killing things with the reversion. But yeah, advance curves that match the cam would be a lot of help.

TF

[fivealive]

yeah old style manifold stock exhaust. i'm poor, sorry. can't afford to buy another cam right now, so I'm just going to put the T back in. One day I'll get a real cam in there.


that's interesting about the distributor advance curves, i did not know that

[MikeHardy]

Originally Posted by dl242gt

You can do this or that. But even Volvo realized the B cam isn't as good for a turbo engine than the A cam. This is most likely why they went to the A cam when they introduced the B230ET instead of using the B that was in the prior B23ET. Try an A in there, advanced a few degrees if you want to use a Volvo cam.

tis true, B23ET and 230ET are pretty similer 405head on the 23, 531 on the 230. same boost, almost the same fuel system (23 just has an earlier version of motronic) but the 230 had 7hp more then 23

[fivealive]

Well, I finally got around to replacing the B with the T, and man, what a difference. The car runs better, idles smoother, and is a lot, lot faster off the line.

Take home message:

B-cam is not a good turbo cam, especially with stock K-Jet engine management.

[BDKR]

Originally Posted by stealthfti

The B only has ~7 thou more lift than an Acam does....and a LOT more overlap. The B doesn't come on until ~3000...if you have a decent flowing exhaust.

The overlap is not helping you out in a boosted context, nor does the later intake valve closing...which lowers the DCR a LOT more than does a T or an A. And with the lower SCR of a B21FT, you need all the DCR you can get.

Advancing a Bcam ~4 degrees might help with the DCR a bit, but doing that will still not do anything about the much greater amount of overlap.

So yeah, you're right: the B is not a good turbo cam, especially in a B21FT.

TF

Wow! Have I had some bad infoz! I've been under the impression for some time that the B cam has "less" overlap then A's. I need another cam!

[Brickster151]

There's a B cam in the orange beasty [b230ft, LH 2.2] - I agree it is a dog off of the line. Past that though it's pretty fine but I still think I might swap it out eventually.

[derosa]

Originally Posted by BDKR

Wow! Have I had some bad infoz! I've been under the impression for some time that the B cam has "less" overlap then A's. I need another cam!

I was under the same impression which is why I installed one in preparation for a +T. To the origional poster even NA it's my experience that the B doesn't have much below 2500rpm.

[MikeHardy]

US engines must be weird.

[nohbudi]

hmmm autotragic... + kcam timed straight up = not nearly as crappy to drive as I assumed it would be... infact... it lags about as much as my old setup did with a tcam... given the compression hit from a cracked exhast valve on the number 1 didn't help... but it essentially feels the same... except it doesn't drop off at 4k.... that just happens to be where things get really interesting... still havn't takin it past 5... spent so long driving on a tcam I'm used to letting it shift early...

[MikeHardy]

thats whats making me thing there not put in properly. i ran a B21A with K cam and that pulled nicely from 2000 up, just got harder and harder with more revs.

B23ET with B cam make peak torque around 3200-3500rpm and are a fairly civilised camshaft.

[Brickster151]

How much vacuum are you pulling with the B cam BTW?

I'm pulling about 15-16in which really is'nt so bad............

[stealthfti]

Originally Posted by ravennexus

thats whats making me thing there not put in properly. i ran a B21A with K cam and that pulled nicely from 2000 up, just got harder and harder with more revs.

B23ET with B cam make peak torque around 3200-3500rpm and are a fairly civilised camshaft.

true, the Bcam does come on above 3100. But the Acam comes on a couple hundred RPM lower, and the Tcam comes on by 2500.

I recently finished up a B to T changeover in a B23F/Kjet. The driveability improvement was considerable. A lot more torque in normal everyday around town driving AND on the highways at legal speeds. MPGs are up as well.
...this in a 245 with AW70/3.91 and with 2.5in exhaust all the way back.

I also did a M to T changeover in a 92 245. Similar results: more torque.

Dale [245gti] said a long time ago that the T is a stump puller in a B23...

It is.

TF

[dl242gt]

Originally Posted by Brickster151

How much vacuum are you pulling with the B cam BTW?

I'm pulling about 15-16in which really is'nt so bad............

If you are pulling 15-16 in hg at hot idle. I would check your valve lash. That cam should be pulling about 18-22inhg at idle. The T cam used to pull about 20in hg and my enem V15 turbo pulls 19in hg at hot idle.

[klr142]

FWIW, I drove a B cam and an A cam back to back on the drag strip this past weekend. Both AT cars, both with stock exhausts, both with modified intakes. A cam was in LH2.4 with no advanced timing, B cam was in LH2.2 with 3 degree advanced timing. The B cam didn't seem to give up much of anything off the line(60ft times were about the same, despite the fact that the 2.2 car was at least 100lb lighter), and continued to pull a little higher up than the A cam did in my car. Advance the timing in the 2.4 car with the A cam, and I'm sure it'd be faster off the line than the 2.2 and B cam car.

In NA mode, the A cam has a tad more torque off the line(down low) than the B cam, which has a bit more torque up top instead. And as others have said, the A cam is the better turbo cam, for obvious reasons. More power down low to get the turbo spooling. May not pull as hard as a B at redline, but it'll be more driveable.

All things considered, I want my V15NA cam back in(this weekend? ), with the ignition and cam timing both advanced about 3 degrees... It WILL pull harder than the A cam timed straight up with stock ignition timing off the line. I just know it. Considering my 60ft times between the A and V15 are basically the same, although my best 60ft with the V15 was done with tires over an inch shorter in diameter.