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Some of this week's Letters to AutoSpeed

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Emissions Info

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The recent article Emissions Regulations - Part Two made for interesting reading given my recent experience with the IM240 test. Attempting to get my Mazda 929 (Series 4 13B turbo engine with exhaust/intake/FMIC mods) through this test resulted in the following results:

Run #THC (g/km) NOx(g/km) CO (g/km) CO2(g/km) Test Result

1. 4.35 0.49 54.52 70.3 FAIL

2. 6.61 0.34 83.1 247.1 FAIL

3. 0.84 1.42 6.7 326.9 PASS

Between runs # 1 and 2, four new injectors and an air pump were fitted to reduce emissions. Instead, they increased! The only change between runs #2 and 3 was the fitment of a new catalytic converter (the old cat was a mere 1.5 years old) just four hours before the test. It's amazing just how much difference a cat can make, and how quickly they cease to be effective!

Damien McKay

2 or 2+2?

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Re your article RB26 260...

Great article - I am a big fan of these cars and have been for some time now. However, the article mentions that the back seats are now non-existent! The Datsun 260Z was strictly a 2 seater - there was another model (the 260Z 2+2) which you may be confusing it with. The photos indicate this car is definitely a 2 seater due to the small gap between the rear shut line of the doors and the wheel. The 2 seaters have become more desirable cars having a lower curb weight. Otherwise thanks for the great article and hopefully we will get an update when the RB30/RB26 engine is fitted!

Dale Everett

Very well spotted! Article now corrected.

Re New Car Tests and Feature Cars...

I've been a regular reader of AutoSpeed for several years now and, is it just me, or has there been a noticeable decrease in new car reviews? Also, the modified car reviews are getting to the point where you can have a template that goes like this:

[Insert Name] bolted on [X Go-Fast Parts] onto [his/her] [InsertCar] and it's all good. They reckon that it's good for a [Insertnumber] quarter mile run.

It would be nice to see some more owner modified cars and more new car reviews.

That said, reviews where you look at a particular model of car over several years (like in The Sporty Magnas) and articles like the Prius modding ones are good reads. Keep up the good work.

Daniel Streefkerk

Points taken. Unfortunately, most of our new car tests rely on manufacturers making cars available – and there haven't been many available lately. Re owner modified cars – we love those cars too but DIY cars that are genuinely well presented are relatively thin on the ground. We feature them whenever we can.

Pick a One-Box

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I’ve been reading with great interest your articles on the Estima The Extraordinary Estima and the Custom vans Hi-Ace Hankering and Van Fan and have a few questions for you:

1 - Which would you choose out of the three you drove and why?

2 - How would insurance be on them - especially the body kitted and18 inch wheeled Estima?

3 - What about the later (mid ‘90s) Delica - they seem to be VERY available but I haven’t been able to find any real info on them!

What would be awesome would be a comparo on a few of them - would make for very interesting reading!! Thanks again for an awesome online read!!

Cameron Tuesley

Tough choice. For sheer interior space the Hi-Ace is superior to the Estima. But the Estima comes with 4WD, looks and feels much more modern and drives better. Overall, we prefer the Estima. We have not yet tested the later series Delica. We don’t think there will be a problem insuring the Estima with a body kit and wheels – but you’d be wise to ring around insurance companies before buying.

Relocated AFM Benefit

Re "Move the AFM?" in Response...

Moving your AFM closer to your throttle body should give better throttle response and more accurate mixtures, as it's measuring the air that’s going into your engine 'now' rather than the air that will go in after about .1sec.

Kent Slaughter

Re Braided Brake Lines #1

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As a long time reader of AutoSpeed I always enjoy your ability to evaluate modifications using quantifiable data rather than just word of mouth and company press releases. Your recent article on braided brake hoses Braided Brake Lines was great in this respect - but I just wonder if the calculation method was correct? When measuring the change in brake hose diameter should you not be calculating the increase in cross-sectional area rather than a straight lineal change? Using this approach sees a change of 4.9% for the old rubber hose, 3.47% for the new rubber hose and 1.2% for the braided hose. Keep up the good work!

Davin Field

Re Braided Brake Lines #2

Your article on braided brake lines Braided Brake Lines is interesting but it misses the point analytically. I have braided lines on my track car because it is the thing to do - but I have always been a bit sceptical about the benefits. Your article gave me a chance to crunch a few numbers which actually support the braided argument quite well. The problem with your numbers is that you look at percent diameter change instead of percent volume change. Given a few assumptions that I had to make (but could be verified with the hoses in hand) the results are interesting.


1 - There are four lines - each 440 mm long

2 - All lines have an internal diameter of 3mm at zero pressure

3 - The change in internal diameter under pressure is the same as the change in external diameter

Based on these assumptions, the volume of the lines at zero pressure and at test pressure is:

Old lines - 12.4cc and 17.5cc

New lines - 12.4cc and 14.0cc

Braided lines - 12.4cc and 12.8cc

If we further assume that the master cylinder has a bore of 2.5cm, the stroke required to expand these hoses is:

Old lines - 1.03cm

New lines - 0.31cm

Braided lines - 0.07cm

One would need to know the pedal ratio to know how much pedal travel is associated with this piston stroke. Also, of course, the test pressures were artificially high but the stroke reduction resulting from using braided lines should be quite apparent at high brake pressures based on this analysis - and it serves to illustrate why a simple percentage change in OD analysis is not particularly useful.

James Mewett

Re Braided Brake Lines #3

Regarding your Braided Brake Lines article Braided Brake Lines - I am surprised that your (perfectly valid) testing showed such a tiny improvement.

I had my 1991 UZZ32 Soarer upgraded just before Christmas 2003 and the pedal feel was transformed. But, then, it probably had the original hoses and I did have EBC GreenStuff pads fitted all-round as well as EBC rotors on the front - so I would have expected to feel a change!

Although, just last week I changed the (probably) original hoses for braided lines on my 1988 Alfa 33 and, with no other changes, there was that pedal feel transformation again...

I say "no other changes" but, of course, the fluid had to be changed so maybe changing the fluid is the biggest single improvement that can be made? Like so much (all?) of the braking system in cars, fluid largely gets ignored - despite the recommendations of the manufacturers.

Barry dal Herbert

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