Of course an increase in octane by whatever means will help, sometimes dramatically, but you dismiss the high boost pump setup probably on some notion that if you can't get peak cylinder pressure before 14 degrees ATDC then you need to turn the boost down. That is about as sensible as saying you need to keep the exhaust manifold pressure lower than the inlet manifold pressure. Nice thoughts, but they don't optimise power on some setups.

An engine dyno is the nearest to what I consider the gold standard, not chassis dynos and not terminals (although all can have problems). There are excellent numbers from a quality engine dyno and they're not good enough for you. There are similar engines holding together not melting exhaust parts. It is not wrong, simply different!

 

Warrtalon I can't argure with you about what you think or don't think about DD numbers. Please remember though I'm quoting results from a car club (the MLR) which has done countless dyno days with huge turnouts for years before evolutionm.net ever existed!

Best I can tell you is that quick Evo 9's in the UK with all the usual parts and about 1.6 bar do around 310 or so on a DD dyno. If you dispute that, I can provide with a bazillion links of graphs to prove it.

 

FYI the graphs on the previous page is data take from DD rollers in Shoot44.

It's from a very neat feature of the MLR called MLR Modified where you can compare dyno results.

 

That's about what they do over here, too. DDs are all the same for the most part...

Why would I dispute that, and why would you challenge me with such a thing? I can't understand what you're getting at...

 

This analogy makes no sense, and represents a failure to understand the relationship between piston position and cylinder pressure.

FYI

 

mommy!

 

FYI you don't have a monopoly on making opinions about combustion

 

It isn't an opinion, but a well researched fact that is published in dozens of treatises on the subject.

I'm happy to discuss piston motion vs. flame front kinetics with you when you're able to demonstrate a willingness to do so.

 

So my opinion is wrong and your opinion is fact because you disagree ROTFL.

I have first hand observational data on the topic of peak power being well beyond the point where exhaust manifold pressure exceeds inlet manifold pressure. I stated this because it is a common misconception, although I suspect it was my assertion about the fallacy of having to drop the boost if peak cylinder pressure peaks later than the ideal that you objected to most. On this my personal data is less good because I haven't used cylinder pressure monitoring whilst mapping, although I do study available literature. What is clear though is that at the point of peak cylinder pressure, a small proportion of the BMEP has been realised and most of it is area under the curve. If I make the peak cylinder pressure 5 degree later but gain some BMEP whilst not melting anything then I will do just that. I have made power on setups that have required what some would consider to be grossly retarded ignition timing. Some of the timing retard is expected because the denser mixture needs less spark advance. Some of the timing advance required with higher octane fuels is simply accounting for differences in flame front propogation. I probably don't need to tell you that the timing advance is no more a measure of output than the boost level. If your pistons, exhaust valves, exhaust manifold and turbine wheel are stout you can make use of more airflow on limited octane by retarding the ignition more than would sometimes seem sensible. If power continues to increase and nothing breaks, then why not? To effectively accuse a very experienced mapper of not bothering to test output at lower boost with more timing advance is the equivalent to telling him how to tie his shoelaces. Of course having higher octane is better, but where it is not practical you end up with a compromise.

Mark Shead's engines have as he has hinted a lot of experience behind them, much of which I'm sure will be making them highly detonation resistant. Yes, he might be fighting low octane to some degree, but it plainly works, making power which some think is impossible on a 4G63 on 99 RON.

I've already alluded to WRC engines which run over 50 PSI boost on similar to pump fuel. I may be stretching the comparison a little far given the materials, restrictor usage, competition engine lifetime etc.

It is slightly odd a Brit telling an American that he thinks that more boost can be better than less boost. I would have always thought it would be the other way around as Americans have a reputation for having/wanting the biggest of everything regardless of subtleties or quality I think that is unfair though and I love Americans

 

So some dont understand how you map a engine on the dyno so I hope this helps the shortend version
Start out mapping at low boost low rpm each time while recording power output progress mapping higher boost with all load points being checked and mapped to the max revs, Finish mapping when you achive your aims so I have tested from min rpm to max rpm min boost to max boost while achiving the the correct levels of Ignition angle and AFR,
So as you see I have tested the engine at all load points so where is the lower boost more power that I have clearly missed .

Mark

 

I stated a well researched, widely known, published fact, not my opinion. Now which part of that statement didn't you understand? If you're observations are as calculated, scientific and fool-proof as you claim, go publish them and refute it.

As far as peak power being produced well beyond the point where the PR is moving in a negative direction, no one has argued this here, and it has nothing to do with what we've discussed here (??). Perhaps you're confused with another discussion.


Later than what and how did you calculate/measure this? You didn't, so there are assumptions made. See my point?

End of discussion.


More like much too far, being that such statement omits a wealth of influential details that are conveniently omitted.

I'll say it again for the benefit of those who didn't see it the first dozen times:

The devil is in the details, and there are a good many details.

 

I think I'll need to ask for your references to back up this published fact. I suspect you are extrapolating what you have read and applying it to other situations in different conditions, but I'm prepared to be enlightened if you're able/willing to do so.

I do see your point about measuring where peak cylinder pressure is, but isn't the basis of your argument that the high boost pump fuel engine is making peak cylinder pressure late, losing power and superheating the exhaust components?

The bottom line is that Mark's shortened argument of how he mapped it is a far better argument that our theoretical wranglings. He is showing gains in power on pump fuel at boost levels where you believe he should be making a loss. You should be asking yourself why (as well as honestly questioning the data)?

 

It seem to keep repeating myself . . .

I'm not questioning data. I'm questioning details, the majority of which have not been offered, yet are pivotal in this discussion.

As for your references, I don't have time for this. Google the following: "mbt 15 atdc degrees", and you'll find dozens of references, articles, patents, etc., that reference this, nevermind what you'll find if you make an effort to visit an engineering library.

 

Ted

Question what testing have you done not read in a book or seen on a internet site,
Did any of this testing if done happend on a engine dyno with you mapping checking your data not from someone else but your own hard work,
Also what is your chosen profession.

Mark

 

Ted,

The builder and tuner of the engine has been on this thread from post 1 pratically. If you had a question to ask why not ask it rather than trying to teach us all why the results didn't happen, or you shouldn't run that much boost, the dyno has low load, DD shoot44 is flywheel bhp, etc.

I'm sorry but all of the above is BS. Bottom line the results speak from themselves. If you don't believe them fine but let other people make up their own mind.