compression ratio with Kenne bell 2.1

[whitelightning]

I'm looking to build/have built a new engine for my 96gt. I obviously will be doing the pi heads and forged internals but I'm not too knowledgeable on the C/R for my build, what type of pistons I need or anything. My goals is to be around 500 Rwhp on pump gas and to have a motor that has moderate boost and compression to be good when off boost but also not detonate while on boost.
I have never built an engine or had one built so I'm sure I left a lot out but any advice would help.

 

[justinschmidt1]

I would say to go with a low compression setup like a 8.5:1....maybe 9.0:1 at the most.

It will be fine out of boost and a lot safer this way.

You have to do some calculations to find out exactly what size dish you need for what compression ratio.

 

[chris91]

Personally I'd pick up a teksid block and 03-04 Cobra rotating assembly. Upgrade the rod bolts to the ARP 2000's and upgrade the pistons too and you'll be good to go. The terminators have no problem going over 500hp so you'll be fine. You plan on going with stock PI heads? If not and if you can't afford to go with the Trick Flow heads I'd recommend the Fox Lake heads. Their stage twos have made me very happy. Also think about cams too. MHS makes some nice blower cams.

 

[whitelightning]

I should probablyadd that I live in California with emissions laws, I live at approx 4000 ft altitude and travel between that and sea level. Also I was planning on going with a new ford racing block just a regular one, a cobra forged crank, Ford racing PI heads (ported and polished) stage 1 comp cams and then the kennel bell 2.1 so that's kinda the setup that I was looking at. All the parts are Cali emissions approved except for the cams but they will pass so I'm not worried bout them.

 

[03DSGGT]

Make sure that you add forged rods and pistons...those two components are more important than a block and crank if your talking boost....

 

[vermilion]

9.x:xx in compression. set of off the shelf emissions friendly blower cams. SCT BA2800 or equivalent maf. let it eat 500hp.

 

[Froush]

Sct ba2800 will give him lots of idle problems at only 500 hp. The 2400 or 2600 would be perfect.

 

[vermilion]

The 2800 has a wider range of tuning vise the 2600.


Sent by smoke signals

 

[rz5.0]

Or vmp hpx in a 3.5 inlet tube.. No trouble at idle and be just fine at 500rwhp

 

[vermilion]

I'll agree. Most ive seen wont use blow thru with a pd. however, i agree it has better resolution and less turbulent spells.


Sent by smoke signals

 

[whitelightning]

Thank you all for your posts. I notice alot of you guys, however, are out of Cali. This is a MAJOR issue because I cant be running Blower Cams cuz the only blower cams I can find are Stage II. Stage I cams will pass emissions sniffer test but ARE NOT legal for my year/make/model/engine. Let me give a basic rundown of what I am looking at doing here as it might help me to help get somebetter feedback, not that any of the above isnt good feedback, but in california tho alot of the stuff cant be on the street.

so what I have got my mind on is

MMR Street Mod 900 4.6 Shortblock (Legal in Cali only b/c its just a forged internal rebuild)
-18cc Dish pistons (cool in cali)
Ford Racing PI heads with 44cc chamber (give or take 1.5cc as the site says) (these are legal in cali and have a CARB approved cert. I am planning on porting and polishing to the max if it doesnt affect emissions)
Comp Cam Stage I (NOT CALI LEGAL) (But will slide by sniffer test)
Kenne Bell 2.1 (Cali legal on Stock 96-98 PI conversion mustangs and 99-04 stock mustangs with boost at 8psi) ( I am planning on running 12# of boost and lowering boost when smog comes around biannually)
JBA or BBK headers either one has to be shorty (I know JBA is CA approved but not sure if the BBKs are)
Bassani Catted X pipe (Not CA approved, will be putting on stock mid for smogs)
SLP Loudmouth 1 (I can run these in cali as cali doesnt really have a big deal with cat backs because they dont affect emissions just noise, so im not worried bout these)
SCT Tuner (Cali Legal)
CAI, MAF, TB (I can swap for CA legal ones if I need to so this isnt really a big deal)
I will put a High flow Fuel pump 255 or higher and a KB boost a pump if I need to (this should be fine in CA)
I will say.....I can only run 91 octane here in cali.
Oh and GTR High performance in Rancho Cucamonga will be doing my dyno/tuning
My cousin and I will be building the shortblock and a friend who is a machinist will do the porting, polishing and Stainless Valve swap and setting


anyway. I just need to know what you guys think for compression on this? I have heard 9.5:1 is safe for 12-14 lbs of boost, I have heard 9.25:1 is good. We all have heard the lower the CR the more boost you can throw at it. thats all fine and dandy but I think I will be running 12# max unless I move to Texas or something but I dont see myself leaving cali ever. also 500HP is just an approx. range. If i get that hey! thats awesome if I only get 440 well thats more than I have now on a pretty stock engine right?
this is my first build, i have a mind for reading and understanding, however math is my weak point. I have read about the Burret and plexi method of meauring compressionand I might would be able to do that if I am shown how to in person and hands on but anyway....what are you guys running for compression? does anyone have a setup similar to this with a S/C at that level of boost? what is your CR?

 

[Froush]

The 2800 has a wider range of tuning vise the 2600.


Sent by smoke signals

The 2800 will most likely cause idle issues without having all that much power. Thats why i would suggest the 2600. It will be more than anything he will ever need for the 2.1. Also, it would be easier to tune. Op, the lower the cr the better for boosted applications if you plan on big boost. Mm&ff's have done multiple articles on kbs with different compression ratios. You will be fine if your tuner knows what he is doing regardless of what you choose. I would suggest something around 9.1-9.2 if you can. Idk whats ok in cali or not though. Personally, im pullied for 18-20 psi through a kb2.2 and am running a 9.1:1 ratio. Will hit the rollers in a couple weeks.

 

[whitelightning]

Thanks Froush, I think for simplicity cuz this is just going to be my street car I'm going with a pretty much stock 2004 PI motor from MMR. The stock Compression on an 04 is 9.4:1. Here in CA a big limiting factor is the 91 octane. I have talked to my tuner and the builder and it seems about 12-14lbs boost is the limit with the 91 and with that compression the new forged (but regular crank) motor will do fine with that amount of boost. Either way I'm sure I'll be happy with it, its more power than I got now on a pretty much stock 96 NPI motor.