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Response

Some of this week's Letters to AutoSpeed!

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"Now Can They Get Over it?"

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I enjoyed the article on the MY06 MRT enhanced Rexie (Revolutionised Rex!) but what made me want to write was the disappointment that this was the only way you could get hold of a current WRX for a drive. I wish Subaru would get over the whole '02 STi thing New Car Test - Subaru Impreza STi) - everyone else seems to have agreed (including owners I've known) that it had a tiny powerband (as you said). Now can they get over it!? Anyway, it's not so bad getting your hands on an MRT car!!

John Masson
Australia

Yes - we’d love to test a standard Subaru 2.5 turbo, but...

Calling Kalmaker Tuners

I was just reading an article that Julian Edgar wrote in Issue 115 (Real-time Chip Tuning) and was wondering if you could help me out. I am looking for a list of all the Kalmaker tuning work shops in Victoria.

Reece
Australia

Check out the site www.kalmaker.com.au and send them an email for the closest agents.

Hindenburg Fact

Just as an aside to Making Things - Part 2... You might be interested in the following link to Dr Karl Kruszelnicki's report on hydrogen and the Hindenburg disaster. It appears it was not the flammability of hydrogen which caused the disaster, but rather the doping compounds used on the fabric. As Dr Karl reports, a helium-filled airship a couple of years before Hindenburg burned up over California with similar ferocity. See www.abc.net.au

Patrick Veitch
Australia

Water Injection for VS Commodore

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Water injection for a stock standard VS Holden Commodore - can you point me in the right direction? I don't need ‘Top Gun’ performance but would like to eek out a few more kilometres from my (expensive) tankful. I've read the article Intelligent Intercooler Water Spray - Part 5 but you only allude to use with a standard naturally aspirated EFI engine.

Peter Riley
Australia

We suggest that you also read Water Injection. If you want to buy an off-the-shelf system we suggest Aquamist products (www.aquamist.co.uk) or you can put together a custom system using brass nozzles, a high pressure electric pump (such as detailed at World's Best Intercooler Water Spray, Part 1) and an intelligent control system (such as a loasensing voltage switch).

Searching for Prius Info

Just reading your articles concerning the NHW10 model Toyota Prius... I have recently purchased a NHW10 1999 Toyota Prius and require as service/workshop manual as no one knows anything about them. The lights on the dash that show ABS, airbag, seat belt and doors won't stop flashing - even when doors are slammed shut. When the car came out here we had to jump start the regular battery to get it going - apart from compliance (where the fog lights were disconnected) this is all that has been done to the car. Any ideas or anyone that I can contact to get it fixed and a service manual for future reference?

Gen
Australia

We suggest posting across the various Prius discussion groups for the best source of English manuals. If you’re in Melbourne, it might also be worth dropping in to http://www.sportsluxurycars.com.au/ - they’ve imported and sold several NHW10s.

BMEP v BMEP #1

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Thank you for your informative article explaining how BMEP is calculated - The Real Way of Comparing Engine Designs. However, I am a little confused by the fact that you calculated your figures based on peak power. Okay, the Honda Civic Type R peaks at 147kW at 7400 rpm giving a BMEP of 11.9 Bar. However, according to my information, the torque peak is 145lb-ft at 5900rpm (excuse our stone-age units here in the UK!). This equates to a power at 5900 rpm of 121.5kW - a bit less than the 147kW peak. Plugging these figures into your formula, we get (121.5 kW x1200) / (2 litres x 5900 rpm) = 12.3 Bar. So the Honda makes a higher BMEP at its torque peak than at its power peak. In other words, if you lowered the rev limiter to 5900 rpm you would have an engine that actually scored higher on your 'measure of how well the design has been optimised'.

This is because the BMEP formula given in the article basically breaks down to torque / capacity, or specific torque. If you are proposing specific torque as a figure of merit to compare different engines, I suggest that calculating BMEP at the point of peak torque would seem more meaningful than at the point of specific power.

In terms of what makes a good engine, I would suggest measuring flexibility in terms of what proportion of peak power an engine develops at half of maximum revs - I think this would give a good feel of an engine's responsiveness in the mid-range (where most drivers spend most of their time). Other figures of merit would be power / engine weight and specific fuel consumption, as you mentioned.

Tom Westmacott
UK

BMEP v BMEP #2

Firstly, congratulations on an excellent publication.

My reason for writing though is in reference to the BMEP article (The Real Way of Comparing Engine Designs), specifically to question the use of peak power in determining the BMEP figure. In simple terms, it is the torque value that represents the efficiency of the motor at any point in the rev range. On a dyno curve, the peak torque figure is usually earlier than peak power. Subsequently the torque figure at peak power rpm is often lower than its maximum, so calculating the BMEP at this point might be understating the true value for the engine. Your formula is effectively converting power into torque anyway by dividing kW by rpm, but possibly using a sub-maximum torque value. Do you agree?

Off topic slightly, I think there is a lot of confusion between, and misuse of, the terms "torque" and "power" - annoyingly so in some motoring magazines. Perhaps you can do an article on this one day (if you haven't already) - I’m sure it’s a perennial argument/misunderstanding.

Martin Sainsbury
Australia

As we said at the end of the article, "BMEP figures don’t tell you the whole story. They don’t show BSFC (Brake Specific Fuel Consumption) and they don’t show the spread of engine torque, the engine’s flexibility or any of those other real world characteristics." Yes, you can calculate BMEP at an engine’s maximum torque output and you’ll typically achieve a higher number -but as always, it's power that makes cars go fast... Re articles covering power and torque – check out Power versus Torque - Part 1 and Power versus Torque - Part 2.

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