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Response

Some of this week's Letters to the Editor!

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Searching for a Dayton

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Hi - I'm looking for the follow up on the MS 5000 navigation article ("The MS5000 VDO Dayton Nav System - Part 1").

Regards

Peter Hedenstr?m
Sweden

Following Part One of the MS 5000 Dayton story comes, wait for it, Part 2 (at "The MS5000 VDO Dayton Nav System - Part 2"). The best way to find a specific article is to enter a key word into the search facility at the bottom of each page.

The Elusive Pipe

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In the article when you were modifying the VL Turbo Intake, you replaced the wire supported convoluted pipe between the AFM and Turbo with another piece. Is there any chance you could track down another piece the same that I could purchase from you. I live three hours South of Perth and have been unsuccessful in many attempts to find a suitable replacement. The one that you used seems perfect - it even had the adaptor to push on the little vacuum hose, is that correct? I would only be too happy to purchase one from you.

Also, my VL turbo is modified and has 270 RWHP with standard computer and an extra injector. By removing the mesh screens, can you see no problem arising from AFM having less restriction or different airflow over it due to restriction removed?

Many thanks and I hope you can help me with my never ending search for replacement pipe for convoluted piece. Keep up the good work - love the tech articles on VL-T.

Matthew Macauley
Australia

That replacement pipe between the VL-T's AFM and turbo must have been a lucky find judging by the number of other readers who've asked to source the same part... If there is no suitable replacement in your area, we'd recommend fitting a 90-degree rubber elbow to the AFM and whipping up a steel pipe to take air down into the compressor (joined to the turbo by a short length of straight rubber hose). A 90-degree elbow can be bought from most turbo specialist shops and the steel pipe into the compressor should be within the abilities of any good exhaust shop. All you need is a 2 ½-inch mild steel section of pipe crushed down to suit the diameter of the compressor inlet - oh, and small diameter fittings also need to be tapped into the side of the pipe.

If all this sounds too time consuming, contact AVO in Melbourne (+61 3 9584 4499) for one of their silicone AFM-to-turbo replacement hoses.

We can't imagine removing the AFM screens would cause any problems but - just to be sure - we'd check air-fuel ratios and ignition timing before and after the mod.

Butterfly Spreads Its Wings

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Hello, I'm writing in response to your 'Pure Pipe Perfection' articles where you install and test a VariFlow butterfly valve. As best I can tell, these articles are from 1998(?), or at least one of the butterfly things on your site is. I'm interested in picking half a dozen or more of these up for our MR2 Car Club here in the 'states. I'm just wondering if they're still in business, and if they sell to the public.

Dmitri Pappa
America

The VariFlow valve we tested in AutoSpeed was back in early 2001, and the valve - we're told by the designer/manufacturer - has since been improved. The man behind the product is Kevin Davis, who's in Sydney Australia. He's certainly still in business and, yes, he does sell direct to the public. His mobile number is +6 409 288 347 (or 0409 288 347 for Australian callers).

Up Front Cooler?

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I currently own a MY94 WRX fitted with an imported '96 STi engine, which has had no modifications other than a full length 3-inch exhaust system and K&N air filter. The standard boost pressure for this engine is 17 psi. I am considering fitting a front-mount intercooler as the factory top-mount is quite small. Are there any disadvantages to a front-mount 'cooler? Will it increase the spool up time for the turbo? Is this type of modification legal or will it cause any hassles with insurance companies? There are plenty of articles about the benefits of this type of intercooler but I - and perhaps other WRX owners - may be interested in any problems they may cause. I find AutoSpeed to be very interesting and informative and would greatly appreciate any advise on this matter.

Daniel Walker
Australia

Fitting a front-mount intercooler to a WRX makes a lot of sense - there's vastly less heat soak affecting intake air temps and, of course, there's space for a huge core that gives minimal flow restriction and maximum charge-air cooling. As you implied, however, there are some downsides. Depending on the specific core and the plumbing used, we'd expect a front-mount intercooler to induce noticeably more lag. A couple of the AutoSpeed feature car owners have made passing comments on this. In addition, the obvious aftermarket appearance of a FMIC on a WRX could lead to problems with legalities and - to boot - many insurance companies throw a wobbly whenever any mods are made to a WRX. Best to ring your insurer and ask, hypothetically, if there are any problems. In our opinion, an aftermarket water-to-air intercooler - in the standard top-mount location - should perform very well in a street application.

Gimme a Boost...

I read with great interest the articles relating to the boost control system that was installed in the Audi. As I work in the pneumatics field, I fitted a very similar system - using SMC products - to my RS Liberty when the factory electronic boost control solenoid failed. I then had problems stabilising the max boost pressure, which was varying quite a bit. Following you story I sourced the Norgren components, but have found that the problem still exists (ie pressure continues past 14+ psi, occasionally triggering the over-boost cut). I have the reg set to 11-12 psi.

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I have recently run a series of tests on the car that gave some interesting results. Among other things, I fitted a highly sensitive flow data logger to the compressor outlet, as well as two electronic pressure sensors (manifold pressure and wastegate line temp) and two temp sensors for inlet air temp and oil temp. I then ran the car over the course of an hour in various situations to give differing engine loads etcetera. The outcome of all this, in brief, was:

a: The regulator works perfectly with relation to wastegate line pressure.

b: There is a difference in turbo spool up time depending on oil temps as well as the turbine max rpm.

c: The inlet air temp directly has a bearing on manifold pressure.

d: The flow rates out of the turbo vary greatly depending on engine load (and inlet air temp), even when the manifold pressure remained constant.

From the testing I was able to gain some conclusions - one being that I can confirm your suspicions re "...but a portion of the extra exhaust gasses being produced under load will spin the turbine faster." I asked myself why this phenomenon was not present on the Audi and concluded that the factory external wastegate fitted is able to flow far higher amounts of exhaust gas than an internal wastegate such as those fitted to the RS.

I also asked myself whether it was worth all the effort doing this and concluded 'yes' because I now have a better knowledge of how my car works - more, I reckon, than the boys at my local Subaru dealer who tried to tell me the turbo needed rebuilding! Anyway, please keep the stories coming; I really enjoy the diversity offered by AutoSpeed and can often be found logging on at midnight of a Monday night for my weekly fix! Many regards.

Jon
Australia

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