Im currently in the process of building a fully built high compression b20vtec that will be running around 12.5:1 compression, and the shop who i am having build my bottom end and possibly tune it once its all done, is telling me that they'd like to see my car tune and run on E85. Now, i wouldnt mind running on it, but i live in GA and there is only ONE e85 station that is anywhere near a reasonable driving distance if i should need a fill-up. That doesnt give me peace of mind especially knowing that there is the possibility that they could just easily cancel their orders of E85 and leave me high and dry. Im also not too happy about hearing the fact that i may hafta run 550cc injectors if i want to run e85 also.

I personally want to tune on pump-gas, but the shop has also told me about the possibility that if i were to get a bad batch of fuel that it could kill my block as well.. so i am not sure what to do. I've heard of a lot of people running 12.5cr on pump gas but how reliable can that be?

Here are my specs:
-84.5mm 12.5:1CR Supertech pistons
-Eagle h-beam rods
-ACL race bearings
-Skunk2 valvetrain
-70mm AEBS throttle body
-ITR manifold, port-matched to TB...(should i get an Edelbrock...?)
-injectors (???) unknown yet...
-ARP headstuds
-GE vtec conversion kit
-Megan Racing 4-2-1 open header
-8lb lightweight flywheel
....cams? [choice btween Pro2s,ITR, or oem b16a2]
....port/polish/valvejob(???)
....stage2 clutch [Competition, Exedy, ACT]


Im trying to make anywhere between 220 - 240max to the wheels, on pump gas.

 

Ditch that POS header and invest in something that will actually make power, buy the Pro2 cams and have a reputable tuner tune it on 93 oct.

 

Your shop is right, 12.5:1 is too high for regular pump gasoline.

People have made 12.5:1 work with pump gas, (or at least they thought they did) but you have to essentially compromise the tune to keep the engine from detonating and you loose the benefits of the higher compression. Those same people have actually picked up a lot of power by dropping the CR a full point!

If you think you have 12.5:1 because that what the piston manufacturer said you would, then you probably don't. You won't know for sure until the block is machined and the head is ported. Only then can you take the measurements to calculate your true CR.

 

I see what you mean about having to compromise the tune to keep the engine from detonating on pump gas, but just because the tuner will have to compromise the tune and have the motor make less power on pump gas still doesnt mean that I automatically won't make my power goal does it?

All it means to me, is that the engine will still have a lot more potenial if i were to re-tune on a different fuel, does that make any sense?

 

It makes sense that tuning on E85 with 115ish octane level will decrease your chance of detonation and compensate with timing to make more power.

If this is what your performance shop is telling you, i would listen. they are the ones going fast at this point, not you!


Edit: your WHP goal is 240.. HP is made up number based on torque and engine speed. It doesnt matter. you should be wondering where your torque curve should be and making sure it doesnt fall off.

 

I dont see why they would make you do anything, that car should run fine on pump gas..

the only place you'd really need to compromise the tune is the lower rpm...

b20's are **** to low rpm/high load knock which can crack a sleeve. Running the proper spark plug and having the proper gap along with having a good tuner you will be fine on pump gas..

Plenty of peoples run 91 or 93 octane with 12.5+ CR.

 

I have built/ witnessed several people with roughly the same CR with a similar setup use pump gas. I am also in the same boat as you, we only have one corn station in my area.

 

You could make it work with 12.5 on pump gas. If you are really worried about it, you could run a headgasket that is a little thicker that will reduce the compression ratio a small amount. But the easiest thing to do would be to get a really really good tuner and let him have at it.

 

Wat spark plugs and gap would u refer us to if ya don't mind me asking??got a similar build..sorry if thread jacking

 

what tuner/shop are you using?

 

ngk7's, start gapping @ .035 work your way down.. learn to read plugs to help determine heat range.. your tuner should be able to do this..

I'm @ 13.0CR on pump gas, i run ngk 8's @ .032

 

THNX ALLMOTOR!!!!

 

You can tune it to run, but again, it is not ideal.

On these engines with higher than 12.5:1, what were the ignition maps like versus a similar 11.5:1 CR engine?

 

i would like to know what would the hp difference be running 12.5:1 vs 11.5:1 in the same motor on pump gas. isn't the average difference per point of compression about 10 hp

 

Pump e85 is 105 octane. E98 is 110.

 

Honest question?

My motor right now is running 29* WOT 3 degrees retarded off of a stock p30 map. According to the plugs, i can probably go a few more degrees.. but i dont know if i want to.

"most" and i say most b series motors are going to like 29-34 degrees WOT, this is a NA standpoint..typical b series builds will like 30-32 depending on mods, cams and compression.

Now, compared to my girlfriends bolt on, stock jdm gsr. Her car is running @ 33 degrees, seems to like it there.

MOST of the motors i've tuned that have been 12.5CR or high like 27-30 degrees total timing. The ONLY place i've had to take timing away was from lower rpms.. the stock ign maps have almost 38-43 degrees in some areas, and i've had to pull roughly 5-8 degrees timing out of that..of course anyone educated should understand on a built car, or a stock car, you shouldn't be mashing the gas in 4th gear @ 2500rpms.

 

I love high compression setups.. but i do recommend that for most people 11.5-12.0CR should be the ideal CR for a street car. The power gains just from CR aren't alot.. but it expands the area of mods that can be ulitilize.


A h22 would only need 11.0CR to run pro2's or pro3's and really take advantage of the cam profile because of its displacement..

A b18c would need at least 12.0CR+ to really take advantage of a pro3 type profile.

Its a rough guess, and yes, compression is only 1/10th the equation for power but it does help.. Most people dont realize its a trade off, the bigger the motor, the less compression you really "HAVE" to run.

 

YOu'd have a better chance of getting bad gas from E85 than you would from pump gas. Pro2s with an ITR manifold? Kinda of a bad match here. Same with the megan header

 

Man Im runin a fully built hc motor as well its 12:2.1 and im runin 91 with 3 liters of VP 110 mixed in and it runs good super strong!! maybe give that a shot? Cuz i feel ya with e85 its not close enough!! Good Luck

 

this is correct. on my det i ran 7s. on my high comp e85 sr im running 9's and may switch to tens on the dyno.

e85 is a good fuel to jump to if you have it avaliable. its 115 octane comparable, granted you have to run more. its knock level is lower and you can really run an aggressive tune.

if you can, do so. take your shops advice, you will make more power then pump if your knock limited.

stratton.

 

OP must not want to hear "oh youre running e85???? yo that **** is garbage!!! EATS FUEL PUMPS AND INJECTORS"

 

lol im running pump gas (91) on 12.5 comp
i got a jdm itr with ctr pistons
just have a gooooooood tuner that knows what hes doing then you'll be finee
if you were around the socal area id tell you to go to RACELINE and have elton tune it.