BC stage 4 288 cams

[hotboykemarm]

i got a set of bc's and i'm building a 2.3 stroker i'm wondering if i have to clearance the pistons for the cams, let me know your opinon on the 288 cams.

 

[JayRolla]

Not sure about the first question but I dont know they are good cams. In a stroker they will act more like 280's woudl in a 2.0l.

 

[interex]

That's not exactly right either. Honestly if you're going to use 288 cams you better be building one heck of a monster for race application only. Those cams are not made for street application, will be too agressive for your engine and you will have a very crappy power curve for a daily driver.

 

[JayRolla]

I very disagree. Running 288's in a stroker are like 280's in a 2.0. I would myself go with 280's so they wont be so aggressive and you shouldnt be spinning that stroker too high.

I know someone running 288's and they gave him a lot over his 280's but this is on a 2.0 revving to 9k. They actual idle pretty good around 1000rpms.

 

[interex]

I still say 288's are too much. And I can almost promise you won't be pleased using them. I chose 280's for my 2.3L and am still worried it may be too agressive for my application.

 

[andy4g63]

Nope they are not. I have the 280's on a 2.0 liter and I have powerband from 4700rpm to 8300rpm and the car keeps pulling like freight train. The powerband is actually feels wider, this is from whe I reach full boost to redline.

 

[JayRolla]

I still say 288's are too much. And I can almost promise you won't be pleased using them. I chose 280's for my 2.3L and am still worried it may be too agressive for my application.

Ohh no you will be happy with them. Maybe want even more. Putting 272's didnt do really anything to my buddys stroker. The stroker likes the more aggressive cams. The only reason cams can be to aggressive is if the turbo is too small.

 

[hotboykemarm]

i'm going to be using a t4/t67 with divided long runner manifold, ###### at 25psi on meth and reving about 8500rpm fully blanced, forged internals, ported head, full ferrea 1mm oversize valvetrain intake and exhuast side with dual springs titanium retainers, etc. it shouldn't be that bad as long as spool up is around 3700 to 4500 i'm good.

 

[andy4g63]

i'm going to be using a t4/t67 with divided long runner manifold, ###### at 25psi on meth and reving about 8500rpm fully blanced, forged internals, ported head, full ferrea 1mm oversize valvetrain intake and exhuast side with dual springs titanium retainers, etc. it shouldn't be that bad as long as spool up is around 3700 to 4500 i'm good.

The only person I know to run the BC 288's is a guy here on forums:

His name is 95GSX racer, he has a wicked RWD car, that runs 8's, so feel free to ask him.

 

[spydermanX98X]

Yea i hope your car will never see the street if you go with 288's i think 280's are fine unless you want to run liek above mentioned, 9's

 

[dsm-onster]

Duration has nothing to do with rpm. And everything to do with piston velocity. If the 288cam is used on a 2.0L and the peak power is at 9000rpms, then for the stroker motor the peak power will be close to 7600rpms. This is because of the velocity of the airflow is the same between the motors at these different points. He!! this is the reason why strokers are better, more air earlier. You HAVE to have more velocity. And duration utilizes the momentum of the air. Momentum is directly proportional to velocity. The stroker motor piston has to cover more swept volume faster per revolution than a stock stroke motor. This stroker piston velocity is approximately 15% faster than a stock stroke piston at the same rpm. And therefore it takes only 85% of the rpms for a stroker to have the same air velocity as a stock 2.0L motor. The air velocity is closely proportional to piston speed.

http://www.dsmtuners.com/forums/cylinder-head-short-block/296409-hks-272s-vs-briancrower-280s-2.html#post151523066
http://www.dsmtuners.com/forums/newbie-forum/292567-precision-turbo.html#post151485514

You don't need a "wicked" race car build to run up to 7600rpms. What is the stock rev limit anyhow. . .

 

[delta448]

Were you just using 9k as an example, or is that actually a fairly close estimate to the peak power rpm with 288's, a 2L and a proper turbo choice?

Just wondering, I was thinking that peak power would be a little higher up, -depending on overlap/adv./ret. of the cam gears of course. Does anyone even make a longer duration than a 288?
Not saying I'd ever be willing to hit 8.5k+ with a 100mm stroke and 1.5 RR... but if someone did... ?

 

[dsm-onster]

Pulled that number out of thin air. It could be close. 272s peak out at 7-7.5K from my experience if you have a smim more towards the 7.5K end. 280s seam to peak at 8.5K from everyone I know using them. Both these cams have plenty of usable power after those peaks. I don't have any first hand experience with 288s. Would the peak out at 9.5K? I don't know. I'm sure they would have plenty of power after 10K.

 

[andy4g63]

Were you just using 9k as an example, or is that actually a fairly close estimate to the peak power rpm with 288's, a 2L and a proper turbo choice?

Just wondering, I was thinking that peak power would be a little higher up, -depending on overlap/adv./ret. of the cam gears of course. Does anyone even make a longer duration than a 288?
Not saying I'd ever be willing to hit 8.5k+ with a 100mm stroke and 1.5 RR... but if someone did... ?

BTW, could tell me what the Rod Ratio is on 2.0; 2.1-destroked; 2.2 destroked; 2.2, 2.3 2.4 strokers?

 

[delta448]

BTW, could tell me what the Rod Ratio is on 2.0; 2.1-destroked; 2.2 destroked; 2.2, 2.3 2.4 strokers?

Sarcasm?

There are many different possible combinations of rod length and stroke length. You could have about 4 different combinations just with off-the-shelf parts on an engine displacing 2.1L. Then think about all the different combos that could be with a 2.2L using a 94mm Eagle crank, since the rods or pistons or both have to be custom to use it.

The formula for rod ratio is just to divide the rod length by the stroke length. Example: stock 2L uses 150mm rod and 88mm crank, 150/88=1.70.

 

[dsm-onster]

The above math and this chart thanx to TunaTalon is all you need to ballpark this. If you have a stroker setup and you have a dyno chart, you can do the math and see where your power peak would be approximately is you switch back to a 2.0L and vice versa.

Note: a long rod motor (4g64 with stroker pistons and 6mm longer rods) has a piston speed that is very close to a stock 2.0l 4g63 motor there is about 70 rpms difference at 8K. This means that a long rod de-stroker is just as hard on wristpins as a 4g63 if all you're looking at is rpm. However, the stroker pistons used in such a setup, which have shorter wrist pin height, is 15% less in weight than the same manufacturer non-stroker piston, which has the stock wrist pin height. This is what widens the gap of a destroker motors safe rpm limit. The tension forces acting on the rod bolts are much less at the same rpm or the same at a much higher rpm. If arp clamped forged 2.0L internals can handle 9000rpms all day long, then the same manufacturers long rod destroker/rods pistons can handle aproximately 15% more, or 10350rpms. And remember there is not much loss in velocity of the piston running the long rod destroker, only about 1% (70rpms / 8000rpms). The extra .1L of diplacement certainly makes up for this. A destroker 2.1 has the same power band of a 2.0L but can handle much higher rpms and has 5% more displacement which DOES increase torque.

What is scary is that a 2.0L motor with good internals can see 10K regularly. This means that a 2.1L destroked version can see 11500 rpms regularly. A 2.1L motor with that revlimit can see 20% more power than it's 2.0L counterpart. 288s would work well in this setup for sure. And a VERY large plenum intake manifold with VERY short runners would be on order.

Kiggly: DSMLink User Group Forums reply.

288s would peak at a lower rpm with a stroker, or a long rod destroker would be able to utilize the powerband of the 288s better than a 2.0L.

 

[andy4g63]

Sarcasm?

There are many different possible combinations of rod length and stroke length. You could have about 4 different combinations just with off-the-shelf parts on an engine displacing 2.1L. Then think about all the different combos that could be with a 2.2L using a 94mm Eagle crank, since the rods or pistons or both have to be custom to use it.

The formula for rod ratio is just to divide the rod length by the stroke length. Example: stock 2L uses 150mm rod and 88mm crank, 150/88=1.70.

No, man, there is no sarcasm at all. You posted before on Holset thread and I see, that you are very well informed on that matter, so I just asked you. What is supposed to be the rod lenght on a 2.1 with 88mm crank and on 2.2 destroked with 94mm Eagle crank. What kind of pistons are available for the 2.2 destroked??? Thanks,Andy.

 

[delta448]

What is supposed to be the rod lenght on a 2.1 with 88mm crank and on 2.2 destroked with 94mm Eagle crank. What kind of pistons are available for the 2.2 destroked??? Thanks,Andy.

I don't want to get too off-topic in this thread, so if you have another question maybe we could just start a new thread, but anyways I'll try to answer this question as best I can.

The crank throw length, rod length and piston height have to add up to the same amount as the stock combination or the compression ratio will change dramatically. You also have to consider if stroke changes or not since it affects the amount of volume being compressed into the same combustion space and then the piston is dished or domed appropriately to get the desired CR. Other than that, you can use any combination that can be manufactured and adds up to the same length as stock.

For an example I'll use the most popular version of a 2.1L destroker.
So, looking at the stock 64 rotating assembly you see a crank throw radius of 50mm, a rod length of 150mm, and whatever the stock piston height is, which doesn't matter that I don't know right now. I know that I can move the piston height as much as about 7-8mm maximum without destroying the piston's strength too much to use it (8mm is really pushing it). Off-the-shelf 63 block 2.3L strokers use a piston with a 6mm shorter height.

That means with an 88mm crank (44mm radius instead of stock 50mm), and a lighter weight stroker style piston with the wrist pin moved towards the top 6mm, you'd have an extra 12mm (6mm less stroke + 6mm less piston height) that could be added to the rod to improve the rod ratio. So now you end up with a 162mm rod length and 88mm stroke giving a 1.84 RR. The 2.1L maintains the same average piston speeds of a 2L, but offers less side-loading, more piston dwell time and more displacement.

 

[andy4g63]

Thanks, man. Your help is very appreciated.