Compression Vs Fuel Type

[trikesrule]

I realise we've touched on parts of this subject before but I need to understand what works in the real world. I feel a specialize thread is in order. Some of these people here in speedway are trying to run 14:1 on BP Ultimate with Octane Boosters. But are they trying to get too much out something thats not designed to cope with such a high load? Can a single throat carby cram enough air in to service these high compressions? What are your thoughts?....trikes

[Chris Y]

BP Ultimate is what? 98 RON?

I guess it depends on the advance, but I tend to think that 14:1 is a little high for such an octane rating. However, from your other posts, I don't think you're suffering from too much detonation (as you seem to be running quite a rich mixture, probably because of the relatively small carb), and your problems are mostly due to warp of cylinder heads/blocks and inadequate head gasket sealing/strength..

From this, it would seem that you either need to run a tougher head gasket, or reduce the compression a little. With the single throat carb, you have to wonder if you can get enough air in to make that amount of compression worthwhile?

[phoenix]

Isn't it possible that running through the restriction of a small a single carb results in the cylinder to only be partially filled?

If that is the case, despite the apparently high static compression ratio the dynamic compression ratio and the peak compression pressure is no more than that of an easier breathing engine with a lower static CR? For example, 80% cylinder filling (i.e. internal cylinder pressure of 0.8 bar just before the inlet valve closes) would result in an effective static CR of 11.2:1

The current breed of WRC engines with turbos breathing through a minute restrictor have resulted in static CRs considerably higher than would be expected for turbo engines for this very reason.

[zefarelly]

I'm rebuilding my engine now, it'll be a static CR of 12:1, this cam . . .which will reduce the effective CR I know

DURATION @ 0.1mm Valve lift : 322 ° 322 °
DURATION @ 1.0mm Valve lift : 274 ° 274 °

I run a mix of posh petrol (Sunoco 6RSR) and unleaded to maintain 100 octane minimum, or at least thats the theory.

A cometic head gasket betwixt block and head with ARP Stud kit keeping everything cosy and together

I'm hoping for at least 140 BHP and not much less in torque between 4k and around 8k RPM.

much higher than 12:1 and I think all sorts of other problems will occur as well

[trikesrule]

I'm wondering about what the mototuneusa guy has said regarding his hi-velocity intake ports vs what port shape we run now. Stopping or reducing the fresh charge from exiting the cylinders by he says by altering the port shape (smaller) and increasing the velocity by upto 30% has merits. Check out the above site please guys and lets have a chat. Zefarelly sounds like a good mix of components and ideas but do u need a new engine? I've always found that my car(s) (gravity racers) were faster down the straights if I found ways to get through the corners quicker.......trikes

[1200Datto27]

Originally Posted by phoenix

The current breed of WRC engines with turbos breathing through a minute restrictor have resulted in static CRs considerably higher than would be expected for turbo engines for this very reason.

A friend of mine builds engines for rally cars, running a 34 mm restrictor, and he usually has the CR's around the 11:1 ratio. He built one of these engines without the turbo(but left the restrictor in place), and it made 90% of the turbo'ed power, but only 40% of the torque.

[trikesrule]

A/F Ratios (Stoiciometric) whats ideal on unleaded (BP Ultimate)? I was led to believe the magic number was 12.9:1 but our engine man said he'd like to see it about 14.4. I don't know. What are your thoughts?

[greenamex2]

My previous incompetent engine builder inadvertently set my CR to over 14:1. Running on Super unleaded it gave about 190BHP.

Correcting this to 12.5:1 it then gave 218BHP.

The ignition timing to compensate for the higher CR was losing BHP.

I suspect if I used octane booster it would have made at least 218BHP with the higher CR but the thing blows up often enough as it is, octane booster costs money and I can't be bothered.

[johnny yuma]

I was speaking to a long term Shell manager here in Australia,he said
all pump unleaded is manufactured as 92 octane here,then octane boosters
manufactured in the Geelong,Victoria plant are used to treat the base product to 98 octane seen at all outlets or 100 octane at selected outlets.
It would seem to me any attempt at further use of off the shelf boosters
on fuel that is already doped up may not result in a higher octane rating anyhow.

[trikesrule]

After what I saw on the dyno today I believe your dead right Johnny. We ran our regular inline six (speedway car) on the dyno and after we had a couple of little fluttery things fixed we made more power with a better grade of fuel (sunoco 104) (many thanks to the people that pointed me in that direction) than any of the Boosters with BP Ultimate. The dyno guy said 'last year when the only way you could buy Ultimate was by the 44/200 lt it was of a lot better quality than what we can buy at the pump' He also said we (speedway) were'nt alone with blowing head gaskets / plug fouling - engines not running right etc. And it all stemmed from the people (me included) thinking that pump Ultimate was still the same as the drum stuff. It ain't the same quality and I heard the detonation (with Ultimate) loud and clear. I'm convinced that good quality fuel is leading me to the light. Now I pray we might just finish some races and get our championship back on track.........trikes

[trikesrule]

Last Thursday had our regular 13.7:1 engined car on the dyno. Had to abort the first run because detonation was so bad. Fuel used was BP Ultimate with octane boosters. Next run was performed with the dizzy pulled hard back. 74kw and lots of detonation and a misfire - not good. Replaced one lead - misfire gone. Dumped Ultimate. Sourced some Sunoco 104 and sorted a needle / seat problem (too small) and the numbers started to climb. After 3/4 of the day the dyno guy said to go racing. And after Saturday nights dominant performance I'm suitably pleased with the dyno chap we used (our first time). He settled on 26 degrees advance with 1.5 degree safety margin. Finished with 100kw at the rear wheels. Hp was down but that may have been the change to a different dyno but the torque was up and we reckon that was probably the fuel switch. Dyno guy explained that Ultimate at the pump is not a scratch on the Ultimate in drums we used to buy. He should know he used to buy it in drums and use it in his turboed circuit car (364kw at the rear wheels). He has been running Sunoco 104 for a few months now and is happy with the level of detonation he is or is not getting. He races with an ear socket connected to his knock sensor so he can listen to his engine when he is racing. How clever is that! During the racing this engine is now the loudest (from the front) snarling torquy grunty beast of a six cylinder I've heard for some years. Perhaps such little amount of advance with this compression (and this fuel) is a better package than the same engine with less comp and more advance. As I said the torque was up and that's what gets us out of the corners so I reckon we will keep it that way. Our regular competition was made to look very ordinary. Thank u very much for the conversations and suggestions chaps........Regards trikes

[Notso Swift]

Originally Posted by johnny yuma

I was speaking to a long term Shell manager here in Australia,he said
all pump unleaded is manufactured as 92 octane here,then octane boosters
manufactured in the Geelong,Victoria plant are used to treat the base product to 98 octane seen at all outlets or 100 octane at selected outlets.
It would seem to me any attempt at further use of off the shelf boosters
on fuel that is already doped up may not result in a higher octane rating anyhow.

If you are in Melbourne it wouldn't have been Ian James by any chance? He like to talk about this, and since he was ex- in chage of Terminal engeneering for this part of the world he knows his stuff.

Anyway that is crap, sort off, yes it is right for Shell in Smithfield and Corio, but PRA in Melbourne, Kiewa in WA and Bulmer Island in Brisvegas all have dedicatd crackers for their premium products. I don't know about Caltex Botany as I have been out of industry for a while. The base spirt is still blended with additive packs to the end users (oil company) requirements, this is usually done at the gantry for shared terminals. Although in Vic Mobil Yarraville (which takes PRA product) doesn't have this facility and BP pull out of there, so the fuel is identical. Caltex use Shells base spirt, however, they have their own terminal and blend themselves.

In Vic Shell stuffed them sleves up by spending up big (over $1b about 10 years ago) on a huge upgrade, unfortunately the market changed on them and Hi-octaines are much more in demand, PRA was a couple of years later and put in a smaller more flexible upgrade ($250m 4 years ago) dedicated to high margin premium products

[Notso Swift]

Originally Posted by 1200Datto27

A friend of mine builds engines for rally cars, running a 34 mm restrictor, and he usually has the CR's around the 11:1 ratio. He built one of these engines without the turbo(but left the restrictor in place), and it made 90% of the turbo'ed power, but only 40% of the torque.

I am on a budget and run mine at 9.5:1 with a 36 mm restictor (circuit racing) and peak boost of 21 psi, but once you hit about 4000 rpm the restrictor cuts the boost out and by 6000 you only have about 5 psi left. Some of my competitors run without a waste gate and let the motor hit 35 psi... gulp... they just let the restrictor pull it down at high revs and work the advance around the boost.
I know a guy who runs an NA form of my motor in rally (no restrictor, of course) and he has more power than my blown example... mind you he has spent 4 times what I have spent and does run it at 11000 rpm to get there...

[johnny yuma]

NotsoSwift-What I know about the oil industry you could engrave on the head of a pin with an outboard motor.My Sydney contact was referring to Shell,our conversation came about due to the recent 2006 TEMPORARY partial shutdown of the Shell Silverwater refinery and the use of Singapore unleaded which is cheap because the big demand in South East Asia is for diesel and they need to sell the petrol that comes out in the process.My contact was not of the view that the big drop in the pump petrol price at the same time was other than a coincidence.

[Notso Swift]

The price equallity is because the wholesale price is (supposed to be) bench marked against Singapore. When there is too much of a gap you have privae operators bringing in tankerloads, which usally starts a price war to stop it happening again (for a year or so, at least)
Wasn't meant to be a flame, what I was trying to point out is that it is only correct in a narrow context and the situation is different depending on which state, or in the case of Victoria with two refineries, producer you source your fuel from.

[johnny yuma]

no problem just curious-cheers

[trikesrule]

14:1 engine and 12:1 engines both racd on Sunoco 101 last night. Both finished the meeting with good results 1st and 3rd. 14:1 is a tad slower on 101 compared to 104 and it ran a lot hotter as well. 12:1 had no temp problems at all. Overall a good result. Our Title is coming up in four weeks think I'll put 14:1 back on 104 for the remaining season.........trikes