Potential power difference with octane changes

topcatcustom · Post by **topcatcustom** » Mon Feb 01, 2010 10:12 am

http://www.mustangandfords.com/techarti ... index.html

Rich passed this link on to me and I was wondering as they only use 92 octane pump gas over there, what could you do with the CR and or timing with our standard super pump fuel, which is around 98/99 octane? And how much difference would it make to power?

RoverP6B · Post by **RoverP6B** » Mon Feb 01, 2010 11:07 am

With respect to the 4.6 Rover V8, the maximum power difference between the LC and HC engines is in the order of 5%.

However the way in which the power is delivered is not identical between the two. The LC engines actually put their power down quicker than the HC engines, so up until approx 3000 rpm or so the LC engines are in front..power wise. After this point the HC engines catch up and then climb higher reaching a maximum which exceeds the LC engines by essentially 5%.

If the EMS is programmed to recognise variations in fuel octane, then running 97 or 98 octane fuel would see better performance I would expect.

Ron.

kiwicar · Post by **kiwicar** » Mon Feb 01, 2010 11:14 am

Hi Tom
Usual problem here, they measure octain to a different set of test peramiters to us, they use a different test engine. However as far as we are concerned for cold weather their petrol at 92 octain is equivilent to about 93 on our scale and in hot a whether about 93/ 94 their 88 is still absoulte Sh1t though

.
Yes using our unleaded petrol (which has alot more ethanol than theirs) you can up the CR by half a point if running 95 octain stuff (pretty safely), using super unleaded you probably only want to add another 1/4 to 1/2 CR point, but can add quite alot more timing (again it has alot of ethanol in it) and use knock sensors to take it out when needed.
The trouble is if you are starting to worry about octain rating and push things much further to fine tune your engine to this extent and to dictate detailed modifications you need very consistant fuel from the pump, and guess what the stuff comming from one manufacturers pump is inconsistant let alone across manufactrurs.
Best regards
Mike

topcatcustom · Post by **topcatcustom** » Mon Feb 01, 2010 11:52 am

Not worried about every last possible bhp as it's too expensive and comes with reliability compromises if every component is working to its extreme potential, I was basically just wondering if you could skim the heads down to get an extra 1/2 CR which would result in a few more ponies. Just the difference between yanky 92 octane and our Shell/BP super 98 octane is a fair bit, so it might make sense to cater for it?

CastleMGBV8 · Post by **CastleMGBV8** » Mon Feb 01, 2010 12:07 pm

Tom,

US fuel is 92 MON which i have seen as stated to be equivalent to 95RON which is our basic fuel.

The best street fuel here is said to be Shell V Power or Optimax whatever the current name is, it has good anti detonation properties so should be good for your blown engine and give you a bit of a comfort zone as far as timing is concerned.

Are you intending to run some sort of on boost retard system, with a blower rather than a turbo you will of course have some boost at all times I suppose.

Kevin.

topcatcustom · Post by **topcatcustom** » Mon Feb 01, 2010 12:39 pm

Hi Kevin, its not for the blown RV8, though I will be using the best I can for it to help det, and I have a MSD boost timing master thing to help with retarding the ignition.

I was more wondering about the difference it would make on the SBF I now have, won't be going crazy on the engine but would like to see between 350 and 400bhp nasp, if US is equivalent to UK 95 then there isn't as much difference as I thought, never mind- was more out of interest! I like the look of the build on the attached link, pretty standard apart from the usual bolt ons and hyperereutectic or whatever they are called pistons!

CastleMGBV8 · Post by **CastleMGBV8** » Mon Feb 01, 2010 2:27 pm

Tom,

If you want it road drivable a 300-350 BHP target might be more realistic and quite economic cost wise.

Is it a runner at the moment, are you going to do a full engine strip and rebuild, I'm not that well informed about small block fords but all the parts are available to make a nice healthy engine, just browse Summit Racings site for all the goodies. Jegs might be worth a look also for rebuild kits either budget or performance with better quality bearings.

Link to Summit for pistons £150-£200 for a set, Summits own even cheaper.

Kevin.

http://www.summitracing.com/search/make ... Rank%7cAsc

kiwicar · Post by **kiwicar** » Mon Feb 01, 2010 3:41 pm

Only trouble with summit is that $30 "international order handling charge" on everything, good place to find what you want, then go buy it from someone else!!
Best regards
Mike

kev_the_mole · Post by **kev_the_mole** » Mon Feb 01, 2010 3:55 pm

good place to find what you want, then go buy it from someone else!!

CastleMGBV8 · Post by **CastleMGBV8** » Mon Feb 01, 2010 4:12 pm

They weren't charging that when I bought my pistons and they actually undercharged me, the ex. rate was then $2/£ then which was nice.

Happy days,

Kevin.

topcatcustom · Post by **topcatcustom** » Mon Feb 01, 2010 4:25 pm

It is a runner, though I'll give it a rebuild anyway. I'm planning a trip to the States in about a year so will try and pack my case with engine parts rather than clothes on the return (I'm sure she won't be very amused

) though if it happens before then I will try and get friends who live over there to get them over to me to save on the international fees!

Pity I wont be able to fit a set of these into my case

http://cgi.ebay.com/ebaymotors/15-15x7- ... ccessories

stevieturbo · Post by **stevieturbo** » Mon Feb 01, 2010 7:32 pm

US 92/3 PON is equivalent to our 97/98 RON

The US do not use MON at the pump, they use pump octane number.

So whilst it may sound like they get crap fuel, its probably better than what we get.

sid447 · Post by **sid447** » Fri Feb 05, 2010 4:18 pm

"The US do not use MON at the pump, they use pump octane number. "

This is correct,

They add RON + MON then divide by 2 = PON

90RON = 86 (PON, USA)
92RON = 88
95RON = 91
96RON = 92
98RON = 94

stevieturbo · Post by **stevieturbo** » Fri Feb 05, 2010 4:51 pm

kiwicar wrote:Only trouble with summit is that $30 "international order handling charge" on everything, good place to find what you want, then go buy it from someone else!!
Best regards
Mike

As much as Ive slated them in the past...this $30 isnt as bad as it seems.

Because this $30 is what appears as shipping costs on the Invoice. Which more often than not, is far far cheaper than the actual shipping costs. So you pay a little lesss duty because of it.

topcatcustom · Post by **topcatcustom** » Fri Feb 05, 2010 5:45 pm

sid447 wrote:"The US do not use MON at the pump, they use pump octane number. "

This is correct,

They add RON + MON then divide by 2 = PON

90RON = 86 (PON, USA)
92RON = 88
95RON = 91
96RON = 92
98RON = 94

Interesting, so they are basically 4 clicks down- or is that offset by the different units used? What does the R and M stand for, and is any 1 more accurate than another or are they just different like farenheight, celcius, centegrade etc?