Optimax (again)

Chris · February 5, 2004, 14:26

I've never put optimax in mine, but that's just because i'm a skin flint and don't like paying for something that's probably all in the mind anyway!
Besides, as has been mentioned, if Toyota wanted to run on that, then they would say so.

I've heard of the engine problems, but hadn't heard it put down to the cats before - I thought it was an oil leak that was contaminating the cats?

markiii · February 5, 2004, 14:35

Has anyone actually checked their owners manual?

Mine just says anything 95 RON or above is fine.

Tem · February 5, 2004, 14:45

Quote from: "markiii"Mine just says anything 95 RON or above is fine.

Apparently it runs just fine even with 91 octane from Russia (at least the same engine in Corolla does). Probably loses some power, but no major issues anyway. Then again, I think every car with a knock sensor should run with lower octane...

Anyway, here's a dyno of my stock engine after about 2 months of "learning" with 98E (that's roughly 99 octane and should be similar to Optimax):
m http://koti.mbnet.fi/temmeke/tmp/dyno.jpg m

I can only assume the +9hp comes from the fuel...

MRMike · February 5, 2004, 15:11

Well my previous car I had for 40,000 miles never used anything but Optimax, as with the 2. It's correct that you can only get a performace adv up to a point, the mapping on the ECU is not configured for anything much higher than 98 ron.

The Higher the RON number though, effectively the better anti-knock properties the fuel has (prevents pinking). This will let the Anti-knock sensors / ECU advance the ignition timing as much as possible without the pistons melting, this in turn provides more power because the pistons are nearer Top Dead Centre and therefore not fighting the piston coming up as much.

What makes me continue to use it is a test EVO did on Optimax, I think EVO are one of the most unbiased mags out there at the mo.
They tested Optimax on 3 of their fleet cars (Civic Type-R, Jaguar XJR, BMW M-Coupe). Shell claims that Optimax 'cleans' the inlet valves of the engine and that heavy constituents in other fuels can leave deposits on the backs of the inlet valves with the poorest quality fuels leaving the most which can lead to a tar like gunge within a 1000miles (EVO, 2002).

In order to form an objective test as possible EVO placed cameras into the inlet tracts to determine if any deposits were present. Their test was to run the cars on 'other' unleaded fuels for 1500 miles and then use exclusively Optimax for a further 1500 miles before taking further pictures of the inlet valves. EVO also recorded the cars' in-gear performance figures before and after the test.

Interestingly when EVO took the initial inlet valve pictures the Civic had the most deposits. This car had been using cheap supermarket petrol (so take heed!). The BMW and Jaguar were relatively clean using a variety of SU and regular unleaded.

The inlet valve pictures showed a marked improvement especially on the Civic whose inlet valves were rid of deposits entirely. The other two cars had very clean valves before the test so results were less marked. For the performance figures the best results were again on the Civic with a loss of 1.19 seconds for 60-80mph in fifth. The drivers of the cars all reported smoother running and a more responsive engine. EVO's verdict? Shell's Optimax does what it says it does, leading to smoother running, increasing performance and preventing build-up of performance-sapping deposits.

(Sorry didn't have a link only the mag in front of me!)

Tem · February 5, 2004, 15:29

Quote from: "Mikeharper2"advance the ignition timing as much as possible without the pistons melting, this in turn provides more power because the pistons are nearer Top Dead Centre and therefore not fighting the piston coming up as much

When you advance the timing, doesn't that move the ignition time to earlier point...meaning the piston is further from the TDC...?

MRMike · February 5, 2004, 15:37

You would need to rolling road and advance the timing like you say to get the maximum effect. To be honest I don't buy it for the performance aspect more the cleaning aspect, and I have to admit thats pretty subjective too. The EVO test was a good indicator of this but again that was only a 1000 miles, after a few thou more it might go wonkey.

Thinking about it the mechanic who works on my old mans skyline said not to put Optimax in for some reason saying it ran too rich with it. Seemed a bit strange but he was pretty adamant.

aaronjb · February 5, 2004, 15:43

Quote from: "Tem"When you advance the timing, doesn't that move the ignition time to earlier point...meaning the piston is further from the TDC...?

If I'm correct then no, because;

The timing is actually set BTDC.. So say the timing is at -15deg, advancing it (mathematically speaking, kinda) actually means moving it to say -13deg (so you're increasing the number), so you actually move it closer to TDC.

If the base timing was ATDC, then it'd all be the other way around.

Ideally, if I recall, the timing should be set so that the advancing flame front reaches the cylinder crown just as it begins to drop away from top dead centre..

Timing is confusing s:D

s:D

aaronjb · February 5, 2004, 15:44

Quote from: "Mikeharper2"Thinking about it the mechanic who works on my old mans skyline said not to put Optimax in for some reason saying it ran too rich with it. Seemed a bit strange but he was pretty adamant.

And the moral of that is not to believe most of what mechanics say s:)

s:)

MRMike · February 5, 2004, 15:46

I know ! and this guy is a racing mechanic that works on the GT car. Don't know what he was on that day. Talking about Optimax i'm off to get some right now, nice day roof down me thinks

aaronjb · February 5, 2004, 15:47

Quote from: "Mikeharper2"I know ! and this guy is a racing mechanic that works on the GT car. Don't know what he was on that day. Talking about Optimax i'm off to get some right now, nice day roof down me thinks

Mind if I ask which garage? Just you saying he's a racing mech makes me wonder if it's one I have heard of (and have in mind) s:)

s:)

And.. nice day? It's peeing down with rain here! s:evil: :evil: s:evil: s:)

s:)

Tem · February 5, 2004, 15:48

Ah, you're right aaron...I mean both of you s8)

s8)

Higher octane means the fuel withstands more compression before self ignition...and more compression is achievef by letting the piston go further...

Think Tem, Think s:lol: :lol: s:lol:

aaronjb · February 5, 2004, 15:49

Quote from: "Tem"Think Tem, Think s:lol: :lol: s:lol:

s:D

s:D

Every time anyone mentions ignition timing my brain starts to hurt!

Anonymous · February 5, 2004, 15:53

Quote from: "aaronjb"The timing is actually set BTDC.. So say the timing is at -15deg, advancing it (mathematically speaking, kinda) actually means moving it to say -13deg (so you're increasing the number), so you actually move it closer to TDC.

If the base timing was ATDC, then it'd all be the other way around.

Nope, you're thinking of advancing the wrong way.

Your basically right, typical timing is set in degrees BTDC, but moving towards TDC is retarding, not advancing the timing. This is because the spark will happen later (retarded) when the timing is moved towards TDC. That's why knocking occurs when timing is too advanced (too early) - the piston is not yet on it's way back down from the compression stroke.

Think of the spark in relation to time, not TDC.

Anonymous · February 5, 2004, 16:03

Quote from: "Tem"Higher octane means the fuel withstands more compression before self ignition...

Erm.. yes, but compression is fixed by the relation of piston to head

Quote from: "Tem"and more compression is achievef by letting the piston go further...

Erm.. no.

The pressure within the cylinder increases massively when the fuel burns and the gasses expand (that's where you get the power from). If the piston is further past TDC, travelling downwards, when the expansion is at its fiercest then there is less likelyhood of knock as there is more volume between the piston crown and head.

Tem · February 5, 2004, 18:09

Quote from: "mrbarney"Erm.. yes, but compression is fixed by the relation of piston to head

I just meant that the compression increases as the piston moves upwards squeezing the A/F mixture...like...if you ignite at 90 degrees BTDC you'll have less compression than igniting on the TDC...

Had to Google a bit s8)

s8)
m http://auto.howstuffworks.com/ignition-system1.htm m
And seems my first thought was right after all. Advancing means igniting earlier...and retarding later.

heathstimpson · February 8, 2004, 07:19

My old man has worked in the car trade all his life so when I was up at his garage yesterday I asked him about this Optimax fuel. He told me that there is currently problems with it long term whereby its doing internal damage to certain engine valve guide seals and injectors. He advised not to go near the stuff while they having problems with it.

Anonymous · February 8, 2004, 09:57

Quote from: "heathstimpson"My old man has worked in the car trade all his life so when I was up at his garage yesterday I asked him about this Optimax fuel. He told me that there is currently problems with it long term whereby its doing internal damage to certain engine valve guide seals and injectors. He advised not to go near the stuff while they having problems with it.

Cheers heath... was going to do a 1000 miles with it to clean things up, but think I'll wait now s:)

s:)

markiii · February 8, 2004, 09:58

standard shell is supposed to have the same detergents, just not the octane rating.

Anonymous · February 8, 2004, 10:42

26,000+ miles from new solely on the stuff which I appreciate is too little to be considered 'long term' but no apparent problems with the engine yet. I have also been using Mobil 1 0W-40 since 10K so am doubly damned s:P

s:P

I did get a lovely red Ferrari sportbags from my Optimax Club membership though s:)

s:)

In my case I reckon the biggest risk to my car's engine is the driver and his driving style s:wink: :wink: s:wink:

mph · February 8, 2004, 13:35

Quote from: "heathstimpson"My old man has worked in the car trade all his life so when I was up at his garage yesterday I asked him about this Optimax fuel. He told me that there is currently problems with it long term whereby its doing internal damage to certain engine valve guide seals and injectors. He advised not to go near the stuff while they having problems with it.

More accurately, it does a very good job of keeping seals clean. The 'issue' isn't Optimax itself, but switching to it after using crap for years. The more aggressive cleaning agents will start removing the built-up deposits around seals that weren't being removed by the poor cleaning agents and that's when problems can start.

Anonymous · February 8, 2004, 13:43

I have never joined in with this coversation before, cos I dont understand it all. I just use super unleaded all the time and stay away from Tescos. However today we where nearly on empty (yep we had the 2 out again with the top down!!!).

And happened upon a garage with Optimax in it (shell aint it). SO thought why not. Filled up.

Now I am not really sure if there was a difference, as I was driving it particually hard today on the dual carrigeways, but I am SURE it did feel different somehow, maybe its in my mind?

heathstimpson · February 9, 2004, 18:58

I've used Supermarket fuel for convenience but have heard some horror stories about the rubbish in it compared to the big name fuels s:shock: :shock: s:shock:

Anonymous · February 9, 2004, 19:14

when the snow came i was forced to fill up an a supermarket... they had super plus 97 ron so i used that, but that tank of petrol the car felt rough as hell... could have just been in my head but it didnt feel right. Put optimax back in as soon as i could!

markiii · February 9, 2004, 19:20

not you rimagination.

the long term fuel map learns. When you surprise it it takes a while to re-adjust

heathstimpson · February 9, 2004, 19:25

Quote from: "markiii"not you rimagination.

the long term fuel map learns. When you surprise it it takes a while to re-adjust

Do you know how much difference there is between say a decent standard Shell fuel and Tescos s:?: :?: s:?: