Hey there NA forums, I recently got my hands on a rolling EJ6 Coupe chassis that once up and running will serve double duty for me as A good weather DD and as fast a car she can be at altitude here My current dd is a fuel sucking Forrester XT. I'm in Colorado so without boost I know to temper my expectations. Anyways thats all besides the point, I have the opportunity to pick up someone's freshly built B20 from a friends machine shop(guy brought the block in 6+ months ago to get the work done then just up and vanished so the shop wants to get as much money for there work out of it as they can since its just been sitting), It has a polished crank, Eagle Rods, and 13:1 CP pistons 84.5mm and best of all what I can only determine is a CNCWERX CSS job done to it.

Anyways I'm only really concerned with 2 things:
1st off even with the CSS on it 13:1 on a stock sleeved B20 seems well to damn high especially for medium DD use, I'm assuming pump gas is outta the picture and I'll have to run strictly E85 which isnt an issue considering its fairly available in my area.
2nd I have my old PR3 Head which is built to Type R spec still shelved from my old CRX..R.I.P., with the 13:1 pistons anyone think there will there be any clearance issue's? I'll probably clay it just to be sure but figured someone here might have immediate off hand experience to share.

Now I personally am not stuck on using those pistons and would honestly feel safer going down to something like 11.5-12:1 but If I wouldnt have to spend the extra coin to switch out Pistons to get this running I'd be all the more happy. After Chassis cost and If I were to buy this short block I'd still have around $1800 left for all the extras ie: clutch, belts, alternator, wiring harness, mounts, ECU, and some kind of exhaust.

Well all let me know what you guys think.

 

Basically thats not a crazy comp. Its all in how the motor is assembled first so if its assembled correctly and all clearances are checked daily driving is fine e85 would make it much better BUT make sure you have the motor tuned by a good tuner who's experienced this is very critical on how it performs and how long it lasts.

 

Oh yeah the motor was assembled with great care(my friend would buy it but he's got shop overhead to worry more about) I'm planning on running a s300 V3 atm but one of my local tuners recommended going for an EMS series 1 or 2 instead would be way better.....thats also what they have more experience tuning and thats the ecu's they sale so I dont entirely believe in going that more expensive route is going to be drastically better. Besides that wouldnt my PR3 head boost up the CR too? when it was originally machined and put back onto my old B16 we saw a compression test numbers jump from 155-160 to 190+ across all four.....although it is fairly coated in carbon still and its been sitting for 5 years

 

The PR3 head lowers the compression compared to the P72 (gsr) head by .3 compression points. The PR3 head has larger CC chambers. Depends on milling done on the block and head too. You elevation also drops the static compression considerably.

 

Yeah that's true for a stock PR3 head as for mine though it's had work on the head, it was machined by .005 and has .5mm oversized flat faced valves, 3 angle valve job an the rest is Type R goodies so it wont loose compression....I think...well at least it didnt on the old b16.

 

If you run e85 it shouldn't be an issue at all.

 

Hah yeah I'm not worried about running E85 just the CR on the B20 and its longevity at it.
Also anyone have any idea what kind of MPG it would get on E85? it will be running a Y80 non lsd trans for the time being

 

You have to account for altitude.. 13.1 cr at sea level is like 12.5 at 3000 ft elevation... also if you can play with thise numbers and lower it a little with a. Thicker head gasket. I bet the 13.1 cr is accounting for a stock thickness HG.

My 85mm b20 build would be 12.6 at sea level but due to my altitude and .040 head gaske it ends up at 11.8.

 

Do u know the dish/dome spec (CC's) of your pistons and the compression height? With that and your elevation you can calculate the real CR at the place where you will be driving your car..

 

Sounds like a fun car tondrive when its all finished.

 

Hah yeah thats the hope, might even consider running 75 shot N20 for a little extra every now an then....maybe. my average altitude is about 6000ft thats one thing I didnt consider. so i was wrong its actually rocking Wiseco K594M845 Pistons

heres the spec
art Number K594M845
Bore 84.5mm / 3.327" (.020" Over)
Stroke 89mm / 3.504"
Rod Length 137mm / 5.394"
Compression Height
30mm / 1.181"
Piston Volume +8.25cc Dome
Wrist Pin Diameter 21mm / .827"
Included Wrist Pins 4130 Chrome Moly
Ring Stack 1.0mm x 1.2mm x 2.8mm

 

Based on those specs @ 6000ft altitude B20 84.5mm with b16 head and .030 head gasket your compression is 12.0:1.. at sea level it would be 13.2:1

With a .040 head gasket at your altitude it would be 11.67:1

 

12:1 is still respectable

 

yeah I'm sure it will be a touch higher cause the head was milled about .005in and it has flat face valves So it should be right around 12.3:1

 

Those few tenths wont be that noticeable on the butt dyno

 

at that range of compression, there wont be alot of advantage with running E85. If its too much hassle for you to run E85 (E85 station too far, more frequent oil changes, less MPG, etc), then i personally would just run pump gas.

Also, I would definitely stick with the Hondata. No need to spend extra $ for the AEM at this point.

 

Need to know piston dome cc and also how the piston sits in relation to the deck. That effects alot too.
If you wanna lower it, Id just run a thicker HG and maybe if needed, have the chambers re-worked...

Yeah, you don't really need AEM. Way overkill.

 

Well E85 is readliy available in my area....theres at least 50+ stations in my town with it so no biggie there.....I'm mostly concerned with avoiding block killing detonation....premium up here is 10% ethanol 91 octane....would that really be good enough? Yeah I'm personally partial to the Hondata systems plus I was thinking of eventually going to Coil on plug setup down the road.

 

13:1 on E85, no problem
13:1 on 91 octane....hmmmm I don't think so.

Hondata and Neptune are both good solid choices.

 

Yeah but I'm at 6000ft+ average altitude so its gonna be closer to 12.2:1

 

You will want to open up the combustion chambers to match the piston size.

 

stock chambers work great, no need to open/modify it.

 

Yeah I may consider doing a fully built head sometime in the future depending on where this ends up.....My issue doing a more machined head is what return I would actually see out of it and most likely it would be more High rpm power which I'm not to sure how happy this B20 would be at pushing 8k+ rpm to make 10%+ extra power at the potential cost of loosing life span I'm going to try an make this thing make max power at as close to 7500RPM as I can.

 

Isn't spot facing a b16 head going on a b20 the right way to do it? I know it works regardless but just wondering.

 

Well I didnt expect this but someone went an threw out an offer of $1200 to my boys shop for that block...about $400 more then he was going to sell it to me at. I'm tempted too match since its still a pretty good deal but damn that's alot more then I had planned for.