goddamnit i want an answer...just bought a 91 Si w/ b21a1..why the hell doesn't it perform like the b20a5 in my beat to hell 89 Si??? What's different? Is the transmission the same in these 2 engines. Doesn't feel like it. Will it be easier to swap a built b20a5 into the 91 than to try and make it perform like it should. THANX

 

first of all maan you need to be a lil less upfront, you can't just demand help cause no one will give any advice. everyone here is doing everyone a favor in knowledge. quit being so mad maan.

 

the B21 is crap, that's why

 

my *stock* b21a1 will toast a *stock* b20a5...maybe your motor is shot.

 

ah, yea..just out of curiosity what is it that makes the b21 crap? assuming you're right what motors can be swapped besides b20 and b21?

 

B20 from the other 3rd gens..... an me saying that the B21 is not an assumption, i have friends that have been through a couple B21s each, when they finally decided to say **** it, and put in a B20, their problems stopped

 

OKAY! now let's say i swap a b20..does it need a particular trans? if so do you know the part # for 5 spd to match b20...know anywhere i can get 1...thanks

 

the trans you have should work just fine

 

The B21/B20 are both the same block, except for very distinctive features.

A) The B21 has the fiber-reinforced sleeve meatrial, which doesn't exists on the B20s. Thus B21s are more prone to burning oil.

B) The B21 intake manifold does not have a 2-stage runner system. It relies on the extra. 1 displacement for torque.

They are not bad motors at all, and stock for stock, should slowly walk away from a USDM B20A5. However, grab a JDM B20A, and that should walk away nicely from both USDM B20A5, and the USDM B21A1.




[Modified by PilotSi, 12:27 AM 12/19/2002]

 

i've had no problems with my b21a1. other than it burning oil. i like it because people say it sucks. and yes the b20 intake manifold sucks

anyways b21a1s r dope IMO of course.

 

a 2 stage intake system is a GOOD thing...anyone know of any sites that have JDM b20s? i checked osakajdminports and some others, no one had them. are they becoming harder to find? oh, 1 more thing who sells them complete with 5 spd trans...thanks

 

2 stage intakes restrict air flow at low rmps...they only open under wot. so tell me its a good thing still. u guys been to preludepower.com yet, lots of 3rd genners there.

 

Explain how a dual-stage runner is bad? By decreasing the size of the ports, you increase the velocity of the intake charge. By doing so, you increase torque. After 4500RPMs, the closed ports then open up to allow maximum overall hp anyways...

Now, the peak hp will suffer because of the slight turbulance of the butterflies, but the increased torque makes for a much more liveable engine. Even H22A/H23As have dual-stage runners.

David

 

i disagree about the butterflies in the b20 intake manifold. they are not necessary and prevent the b20 and b21 from getting the amount of air they need. i can speek from experience on this one. i had the b20 in my 89 lude. when i swapped in the b21, i kept everything the same, except had to use the b20 tranny and clutch setup. a direct bolt up. the b21 manifold was giving me a little trouble, so i took the b20 manifold and removed the butterflies, ported it out, and cut the base of the top half of the manifold off. i put that on the b21 and there was a huge difference. i have a power band of pretty much the whole range until about 6500 rpms, when the motor just loses it's power. as far as the b20 being a stronger motor, that just tells me you have something wrong with your b21. the motor that i put into my prelude pulled noticably harder and walks all over the b20. after i did the swap to my car i raced my friends 89 2.0 with a header and catback exhaust and we were pretty much dead even. now that i have an intake, header and catback exhaust, the other 2.0 preludes around here can't even touch me. the only thing that slows me down a little bit is the added weight for the 4ws that i added to my car. check the compression and make sure your b21 is running right. do a tune-up or check it out. maybe there is a simple problem to your solution. or just rip out the b21 and get the jdm motor.

oh, and for everyone complaining about the oil burning, i have found something that worked for my car and may be worth trying. i was going through 1 qt or oil every two weeks. i decided to put in the lucas oil treatment (use 1 qt lucas and three quarts oil for the correct percentage) and i haven't added any oil in over two months. it is staying full. might be worth looking into! well, good luck guys.

 

Umm...the B21 intake manifold does not have butterflies. Why didn't you just use that on your B21?? Especially if you were swapping in a B21A in the 1st place.

Actually, if you did do a P&P around the butterflies, you will have noticed that the port matching between the upper/lower manifold with the butterflies, was probably very bad. Maruccui over on PO.com cleaned up atleast 1/8" worth of material, that is probably why your motor pulled more cleanly.

A USDM B20A5 is pretty weakk, compared to the USDM B21A1, but a JDM B20A should slowly walk away from a both USDM motors. It has a higher compression and has more torque then both motors.

David

 

my b21 manifold wasn't running right. the iacv and something else was running wrong, so i swapped back to the other manifold. it was doing weird things. and i didn't port and polish around the butterflies, i completely cut that part out and took the butterflies out. car runs great. very strong low and mid range. not as much power at the top as i would like, but still lots of power.

 

**** my b21a1 has 248,875 miles on it no problems at all with it so yeah b21a1 engines do not sux.