Lets here it. Does anyone have a success story with this motor?

 

Is this the old Lude motor?

 

yeah, 90-91 prelude si.

 

what is so terrible about that engine? my friend has an 89 prelude that has quite a lot of power considering it isn't a vtec - and it handles very well with stock suspension. he also had a 90 prelude, 2.1 which was an automatic that could beet mustangs in the 1/4 mile. now what is so bad about that?

 

Doesn't sound like anything is wrong. I now have 2 b21a1's. From what I have heard is that these motors are not usually used for build ups. I would like to hear some physics to back it up .

Anyone using this motor? I'm thinking of transplanting it into a 88-91 civic hatch.

 

GREAT motor for f/i. It's very sturdy; closed deck, and a girdle that extends over all 5 caps.

 

Oh, and the B20a5 is the better engine IMO. It has a better flowing head ( I've been told that anyways), a dual stage intake manifold, and does not use the fiber-reinforced cylinders that everybody blames the poor ring sealing with age on.

Greg

 

The reason for that is the crank needs lots of support. The stroke on the b21, and b21a is crazy...something like 95mm....the piston speeds are atrocious. Plus, with the extremely bad R/S ratio all around power is sacrificed for low end grunt.

 

Yes, the poorest rod/stroke of any honda I've seen, but like you said, it has great low end grunt. There are some who have tried to get good results with keeping the engine N/A; it just doesn't work. Force feed it and you can make a beast. Sure, it may not be a powerhouse, but it is a good motor all around, and the 95mm stroke isn't that crazy, after all, 86-89 accords had the same engine geometry, I'm not sure about the 90-93 F-series engines, but they may have the long stroke too. It just changes the shape and location of the powerband and adds a bit more stress to the engine, which the B20a's can take. Besides, you can probably bump the r/s ratio up to around where an LS is by getting custom rods and custom made pistons with the wrist pin located higher.

Greg

 

Doesnt the b20a have the same block height and bore as all the b series motors besides the b16....so if you swapped an LS crank in there you would have an LS motor......

I like low end grunt, but I love high end power!

 

what is everyone talking about? i have raced and hammered on my friends prelude and it has no low end power at all. as soon as it hits 3000 rpms the thing takes off. it has all top end power. he has done nothing other than a k&n filter and some accel wires. there was no need to adjust anything. he hasn't even put his header on yet, or done a performance exhaust. are you guys sure you are thinking about the 2.0 prelude engine and the 2.1 liter for the 89-91 models?

 

That would be a great mod for this engine; a bump in the r/s ratio, while retaining a great block. But they are the red-headed stepchild of the B series, so I don't know if the cranks are compatible. Then again, Crower's stroker kit offers a modified B20a crank.

Greg

 

I bet the b18 crank is compatable....

And to crxplus...have you driven any honda that had lots of power below 3000? I havent. Maybe we should have said the b20s and b21 favor mid range grunt?

And they may pull up to their redline, but that redline is probably lower.

 

crxplus: From most dyno sheets of lightly modified B21a's that I have seen, tourqe, at the WHEELS, surpasses the tourqe peak, at the FLYWHEEL, of a B16a below 4000 revs. That's why I say it has low end.

 

I think once I get a beater to drive for a while, I'll pull the engine and see if the LS crank fits. That would probably be really worthwhile, but while I have everything apart, I think I'll bore the cylinders a bit to get back some of the lost displacement.

Greg

 

Definatly post back and let everyone know how it turns out.

 

to me, low end power is anything under 4000, and then no power above 4000, like my winter beater, the 1.8 dual carb. that has only low end.

as for the low rpm, my friend's goes to somewhere around 7500 rpms before rev limiter. i didn't hit it when i drove his car. i hate hitting the rev limiter. do you consider that a low rpm? i thought pretty much all preludes had the same rev limiter and tac, pretty much 7500 rev limiter and 8 or 9000 tac (which doesn't make sense, but heah)

 

Yeah, I see what you're saying about low end.

The tach in my third gen goes to 8k and I *think* the rev limiter is around 7400, I've never bumped it before. I'd like to know the exact number though.

Greg

 

so how will it fit physically into a civic chassis? just like any other b-series?

 

No, it doesn't mount the same as other B series.

 

Someone send me an LS crank and I'll see if it fits in one of my two b21a's

mike

 

7500?? Well then he most likely has a different engine then the one we are talking about....that engine you refer to would be the H22...DOHC VTEC 2.2 liter. Yea, that motor definitly has some top end.

 

then what else is needed to drop a b21 into a civic chassis then?

 

custom mounts and brackets. One thing that would be fairly easy is mounting the shifter, as it is cable actuated, there are no shift rods to line up.

Greg

 

i know his car is not the vtec - it is the stock motor for the 89 prelude si 2.0. i am not sure exactly where the rev limit is, but it has to be around 7500, maybe a little less, like around 7200 (like my crx) - he has the same tac as i do in my crx. i was driving his car around 7000 rpm's before shifting, so i know it goes fairly high on his tac.