should io upgrade sc from 45 to 62

[gslender]

Head flow has everything to do with boost (amongst alot of other things). See what happens to the boost when you reach the limit of your cylinder head flow......Boost goes up, power stays the same......

Woz

Sure, when taken to extremes yes.

I see this conversation going in circles... and a few posters seem hardfast focussed on making boost a function of head flow as being the only reason why a person with a M45 on a 1.8 can't get beyond 6psi.

I'm trying to help the OP by saying that he a) might have a boost leak, b) could have options to further reduce the pulley size/increase boost, or c) have a timing/cam problem that is limiting the captive postive pressure due to blow-through (intake -> exhaust).

All this debate over how much a 1.6 vs 1.8 head actually influences this discussion seems to be largely irrelevant as when we get into details, people are introducing extreme scenarios (like comparing a turbocharged vs S2000, or when you max out the head flow as being the top line limit) - all true points, but not relevant for the OP issue.

I don't disagree that at the limit, head design can impact max boost seen, but in the context of the OP's question I don't believe it has any relevance.

Afterall, if the 1.8 engine is only 15% better than the 1.6 (in terms of max power) then how can you explain that the head is 2x better at flowing air if the NA engine can only produce 15% more power, and note that displacement is mostly the reason for the power difference here.. (1.8 is 12.5% more displacement than 1.6).

Nobody yet has been able to explain how it can in the context of the OP's question.

Oh boy

[NitroDann]

You are making incorrect assumptions about flow, VE and peak power.

Dann

[gslender]

You are making incorrect assumptions about flow, VE and peak power.

How so?

[NitroDann]

Im at work. Ill explain properly tonight. Also torque a the factor here, not just horsepower.

Dann

[NitroDann]

You say double the boost?

One car running 6 psi one 12? That aint double The pressure.

14.7+12 / 14.7+6= 1.28

28% more boost pressure.

Dann

[gslender]

You say double the boost?

One car running 6 psi one 12? That aint double The pressure.

14.7+12 / 14.7+6= 1.28

28% more boost pressure.

Dann

Ahhh, so the difference isn't that great now... so perhaps another PSI or two would be equivalent... perhaps not chasing as much of a difference.

Oh, and I think you mean 14.5 + 12 / 14.5 + 6 = 1.29 --- 14.5 PSI = 1 bar or 100 kpa

So 29% more air pressure.

Would still like to understand better where the ~30% difference is being used up... note that displacement accounts for only 12.5% of the space where air is being forced into (and creating the pressure that is seens as positive boost).

So half the difference takes us to nearly 9psi which correlates closer to what I've seen on forums in the UK for 1.8 engines that are running an M45

G

[wozzah1975]

Head flow has everything to do with boost (amongst alot of other things). See what happens to the boost when you reach the limit of your cylinder head flow......Boost goes up, power stays the same......

Woz

Sure, when taken to extremes yes.

I see this conversation going in circles... and a few posters seem hardfast focussed on making boost a function of head flow as being the only reason why a person with a M45 on a 1.8 can't get beyond 6psi.

I'm trying to help the OP by saying that he a) might have a boost leak, b) could have options to further reduce the pulley size/increase boost, or c) have a timing/cam problem that is limiting the captive postive pressure due to blow-through (intake -> exhaust).

All this debate over how much a 1.6 vs 1.8 head actually influences this discussion seems to be largely irrelevant as when we get into details, people are introducing extreme scenarios (like comparing a turbocharged vs S2000, or when you max out the head flow as being the top line limit) - all true points, but not relevant for the OP issue.

I don't disagree that at the limit, head design can impact max boost seen, but in the context of the OP's question I don't believe it has any relevance.

Afterall, if the 1.8 engine is only 15% better than the 1.6 (in terms of max power) then how can you explain that the head is 2x better at flowing air if the NA engine can only produce 15% more power, and note that displacement is mostly the reason for the power difference here.. (1.8 is 12.5% more displacement than 1.6).

Nobody yet has been able to explain how it can in the context of the OP's question.

Oh boy

The point i am making is that making the supercharger bigger may not increase power, which is directly related to the Op's question, and If you read back through my posts you'll notice i asked about the OP's setup, and now I'll respond.

My concern is that making the change to the bigger supercharger won't give you more power. I have emailed Eaton to find out the power figures both superchargers will support, and looking at the 45 figures it should be more than capable of much bigger numbers, but I'll wait to hear from Eaton to confirm that.

It does concern me the boost is so low. What are the diameters of the pulleys? Bottom and top? I agree, there may be something else going on causing low boost, but the power figures look about right for a std engine with that sort of set up.

A larger supercharger is only required when you reach the flow/power limit of the one you already have. If you fit a larger unit without the rest of your engine set up supporting it, then you've wasted your money as other things are limiting your power, and it should have been spent elsewhere.

Cheers
Woz

[gussy]

Once you start getting to 10 psi with an M45 the efficiency gets lower quite quickly due to loads more heat being produced. The M62 doesn't produce anywhere as much heat at similar boost compared to the M45 hence why it's easier to make more power at a given boost level.

[wozzah1975]

Once you start getting to 10 psi with an M45 the efficiency gets lower quite quickly due to loads more heat being produced. The M62 doesn't produce anywhere as much heat at similar boost compared to the M45 hence why it's easier to make more power at a given boost level.

It seems to keeps relating it back to the boost figure. It's not relevant, the power/flow figures are.

The limit could be 10lbs on one engine, it could be 15lbs or 5lbs on another, but what you will find is that regardless of engine size or boost figure, it will be at a certain power figure the supercharger reaches it's limit. Nothing to do with boost.

Woz

[NitroDann]

boost pressure is just a function of airflow and restriction.

just as exhaust back pressure is just a function of exhaustflow and restriction.

Dann

[NitroDann]

Also one atmosphere is NOT one bar.

Its more, its 14.7psi.

Dann

[gslender]

Also one atmosphere is NOT one bar.

Its more, its 14.7psi.

Dann

True. 1 atm = 1.01325 bar = 101.3 kPa = 14.696 psi

I always thought 100 kPa was 1 atm, but it isn't.

Thanks Dann.

G

[wozzah1975]

Ok,

Got an email regarding the sizes and flow rates.

The MP45 is bordering small when fitted to a 1.8 (1840cc) engine, and if you're making 140rwkw now there is probably only another 10rwkw before you reach the limit off that unit, even with other engine mods. This would also explain the low boost level IMO. You may squeeze a bit more boost out of it with a further overdrive, but you just about on the units limit already, so not much point in trying

The MP62 will support up to around 200rwkw+ with supporting engine mods, so if you're wanting to go further with it power wise you will need to upgrade to this item.

I quizzed them on supercharging my engine, they recommended the MP90 for it minumum

So, bottom line, if you want to develope the engine further you are going to need an mp62,

Cheers
Woz

[gslender]

Can you share what you got and why you make that claim? I'm curious how that is worked out as it pumps 700cc per revolution (45cu)... The BMW mini is a 1.6 and it gets fairly good HP out of it!?

[wozzah1975]

Can you share what you got and why you make that claim? I'm curious how that is worked out as it pumps 700cc per revolution (45cu)... The BMW mini is a 1.6 and it gets fairly good HP out of it!?

I spoke at length to someone i deal with that is an agent for Eaton superchargers in relation to sizes and power output, and what was needed for a given application. I don't have anything in writing, just notes from the phone conversation.

On a 1.6 the mp45 sizing would be ok, on the 1.8 it is basically on it's limit,and any further mods to the engine which increase flow only make the situation worse (more air needed).

It was an interesting conversation, as i looked at the flow figures too, as stated earlier in the thread. I would be scepticle about claims of much more power than i stated earlier from the givens sizes. the guys i spoke to do these for a living, and they know what works,

cheers
Woz