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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 3:11 pm 
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Mid-Engined Maniac

Joined: Sun Apr 23, 2006 8:26 pm
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For whatever reason, Aerochargers have never caught on. Maybe for cost or reliability reasons.

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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 3:12 pm 
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Location: Fort Worth, Texas
OrangeCrusader wrote:
Image

Variable vane turbos on a twin-turbo 930 porsche, which is already factory turbocharged, same boost, roughly same peak power, but 100% of the torque available at 2500rpm instead of 4500. Try that on a small engine that has worse boost lag, but a 11k rpm redline. :twisted:


I thought Aerocharger was out of business.

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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 3:43 pm 
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KB58 wrote:
For whatever reason, Aerochargers have never caught on. Maybe for cost or reliability reasons.


The latter didn't help the former much. People weren't very willing to pay that much for something they weren't sure was going to be reliable, but apparently they've got them reasonably well sorted by now.

carguy123 wrote:
I thought Aerocharger was out of business.


The updates on their site are quite recent, they seem to still be going.


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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 4:13 pm 
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Location: SoCal
Corky Bell (the turbo book author) raved on and on about them. His perspective was that the Aerocharger was the perfect device for making a small engine act like a big one. They are (or were) very expensive, which apparently killed them marketing-wise. Don't know about now.

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Midlana book: Build this mid-engine Locost!, http://www.midlana.com/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 4:21 pm 
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i know they used their own special oil instead of being plumbed to the engine oil. From old posts it appeared that many may not have topped off the oil often enough.

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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 4:53 pm 
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KB58 wrote:
Corky Bell (the turbo book author) raved on and on about them. His perspective was that the Aerocharger was the perfect device for making a small engine act like a big one. They are (or were) very expensive, which apparently killed them marketing-wise. Don't know about now.


$2000-2500 apiece, plus a manifold/exhaust, if swapped onto an existing car. Looks very expensive until you look up price for normal new high-end turbos ($500-2000+), then it's not so bad, if the gains are really there.

carguy123 wrote:
i know they used their own special oil instead of being plumbed to the engine oil. From old posts it appeared that many may not have topped off the oil often enough.


Yep, they're self-contained, have their own reservoir and special oil (but they'll give that to you free for a song and a photo, it seems), and given their operating conditions, it's best to keep an eye on them a little more than you would a normal turbo, maintenance-wise. But then again, a BEC track car with one of these would be the sort of car you'd want to be doing regular 100-point checks on, since a lot of parts get used harder than they normally would (though their light weight helps here, you'd still see double or triple what the normal driver sees on a road in g-forces), and to be frank, it's home-built like all locosts, so some stuff will go wrong till you iron the wrinkles out.


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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 6:33 pm 
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Joined: Sat Apr 16, 2011 11:05 pm
Posts: 237
Location: Melbourne, Australia.
We are straying WAY WAY off topic here, but after my great successes with twincharging, I spent about eighteen months trying to get a variable vane turbo to work, it was a miserable most unrewarding experience I eventually gave up on.
I am talking here from the perspective of someone with personal practical experience with VNT turbos.

There are two really huge problems to overcome to get even average results.

First, all the exhaust has to pass through the turbine, there being no wastegate that normally bypasses around half the exhaust volume. Sure, you can limit the boost by tilting the vanes, but the turbine has to be sized much larger than a conventional turbo turbine if back pressure is not going to completely kill top end power.
Porsche overcome this by fitting two electronically controlled wastegates.

The second problem is that, most people believe that to get an extremely low boost threshold all you need to do is close down the vanes forcing the exhaust through a very small aperture at very high velocity.
Try it and see what happens !
Close off the vanes and exhaust back pressure rises to extremely high values.

Stomping on the accelerator, at 1500 to 2000 rpm, I could see 80 psi+ exhaust back pressure, and the engine did not like that, even with 5-10 psi boost. So you need a very well developed and sophisticated control system to control the vanes, Porsche use the engine management system to do it.

If you do a lot of engine dyno testing you might be able to come up with a computer system that can control both the vanes and the wastegate to get good all around performance. Porsche seem to have managed it, but it is far more difficult to do than you might realize.

Garrett and HKS still market their ball bearing turbos as the preferred option for high performance gasoline engines, and Garrett sell the VNT turbo for high performance diesel engines.

If Garrett and HKS can't make a VNT turbo work better than a straight ball bearing turbo on a gasoline engine, do you think you can do what they have so far failed to do ?
Believe me, if it worked, Garrett would be selling VNT turbos for use on race cars !!!
VNT turbos have been around now for over thirty years on diesels, it is very mature technology, where are all the race winners and gasoline production cars fitted with VNT turbos ?

There have been a few attempts at production cars, but they have all been failures. Saab tried it and gave up. Even the genius of Honda engineering, with all their budget and resources could only make it work on their Formula one car, they gave up trying to get it to work on the original top of the range Honda Legend.
Look at the power figures they quote for their "variable wing turbo" compared to an equivalent n/a engine, they are pathetic.
It must have been a great loss of face for Honda engineering to finally admit defeat after all the effort they put into it.

http://dwolsten.tripod.com/articles/jan89a.html

Forget about variable vane turbos for a Locost, unless you can do better at getting it to work than the engineers at Garrett, Honda, Saab, and HKS, and countless unknown hot rodders and drag racers that have also tried and failed to get it to work.
Even Corky Bell is struggling, and he was personally involved with the design team that came up with the Aerocharger in the first place.

I am just trying to save some of you some money and a mountain of grief.
VNT turbos have been the technology of the future for thirty years, but nobody but Porsche have been able to get it to work on a gasoline engine.

Now let's get back onto the topic of 4WD Locosts.


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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 9:48 pm 
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Location: central Arkansas
I've found several pictures of the outsides of Dax Quadras, but nothing about how the 4WD bits are arranged, even on their web site.


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 Post subject: Re: AWD Locost?
PostPosted: Wed Jul 13, 2011 10:04 pm 
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Posts: 237
Location: Melbourne, Australia.
TRX wrote:
I've found several pictures of the outsides of Dax Quadras, but nothing about how the 4WD bits are arranged, even on their web site.


I always assumed it must use the Ford Sierra 4WD drive train, which would probably be a good choice for a British based car.
Image
This seems to be hinted at:
http://www.daxcars.co.uk/rush/specificationquadra.htm


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 Post subject: Re: AWD Locost?
PostPosted: Thu Jul 14, 2011 1:26 am 
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Joined: Fri Jul 02, 2010 1:13 am
Posts: 359
Location: Phoenix arizona
I think an appology is in order here..it was myself that started babbling on about gtr skylines ,twin turbo's and getting us off topic.Just the other night i was chatting with my brother in new zealand about this topic,he owns a nissan stagea station wagon,that comes with a rb25det from the factory,it was auto so he put in a manual box out of a gtr...my point is he is very familiar with 4wd stuff,so he had mentioned that a mate of ours was going to put a gtr box in his 900hp supra and then put in a front diff out of an altezza 4wd ..lexus is300 in the us ,maybee that could be paird up with that sierra 4wd box and use something toyota ,probably supra ,corona ,cressida ..the list goes on that has independent rear so the diff ratio would match ,if not exactly tyre size could adjust the problem,if i remember correctly the 2l bellhousing pattern is the same as a mazda? or zetec? .Another idea i had was polaris razr stuff,all independent ,uses a small belt driven centrifugal gearbox turned sideways ,in the back..driveshaft runs back to front,its all lightweight stuff .just googling altezza diff stuff and found that they are double wishbone front and an lsd is available from rhd japan ,maybee this could fix the backwards rotating problem,im sure they just use standard cv's so it would be a matter of making up hub carriers for the front ,the same as i made for my nissan rear or haynes build ,the only difference being that you would add a peice of steel to bolt a ball joint to so the thing would have steering! .I cant find any images of the stagea front suspension but im sure it will be somewhere.
wayne-o


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 Post subject: Re: AWD Locost?
PostPosted: Thu Jul 14, 2011 2:22 am 
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Joined: Sat Apr 16, 2011 11:05 pm
Posts: 237
Location: Melbourne, Australia.
Skyline 4wd stuff is certainly relevant to a 4WD discussion.
The Skyline GTR/GTS4/Stagea have a few rather interesting bits and pieces that could be adapted to a Locost, as do the family of monster Nissan off road 4WDs.

I will be using a pair of GTR front steering knuckles and hubs.
Pressure cast aluminium with a 5 x 4.5" wheel stud pattern, and fairly respectable brakes.
It is also quite compact vertically, being around seven inches tall, ball joint to ball joint.
All it requires is some fairly simple machining to fit the ball joints of your choice.
Here is a not very good picture I took a long time ago for a bump steer discussion on another Forum, but it does show the Skyline GTR alloy hub carrier fairly clearly.
http://i144.photobucket.com/albums/r166 ... steer2.jpg


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 Post subject: Re: AWD Locost?
PostPosted: Thu Jul 14, 2011 11:12 am 
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The voice of reason
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Location: Massachusetts
Why has putting a reversed Subaru drivetrain in been discounted? It seems by far the easiest way to go. There is a reverse cut ring and pinion for them. Other solutions seem very bulky for a small car like a Locost...

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 Post subject: Re: AWD Locost?
PostPosted: Thu Jul 14, 2011 11:59 am 
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wayne-o wrote:
I think an appology is in order here..


One from me as well, got sidetracked a lot there. Back on topic...

horizenjob wrote:
Why has putting a reversed Subaru drivetrain in been discounted? It seems by far the easiest way to go. There is a reverse cut ring and pinion for them. Other solutions seem very bulky for a small car like a Locost...


The issue was the input shaft being wayyy too short (from the reverse-cut skyline diff) to ever work in the subaru case. It'd require either a custom shaft ($) or a custom case ($$$) to work.

There's a lexus diff from the is250 awd also mentioned in another thread, though it has either a 3.769 4.1 ratio, which is pretty high.


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 Post subject: Re: AWD Locost?
PostPosted: Thu Jul 14, 2011 2:55 pm 
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The voice of reason
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I don't understand. There is a custom ring and pinion made for the Subaru that's reverse cut. People use them for Porsche upgrades, I think.

So you land up with a rear engine AWD. Should work...

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 Post subject: Re: AWD Locost?
PostPosted: Thu Jul 14, 2011 6:31 pm 
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Joined: Sat Apr 16, 2011 11:05 pm
Posts: 237
Location: Melbourne, Australia.
horizenjob wrote:
There is a custom ring and pinion made for the Subaru that's reverse cut.

Any more info on that ?
Maybe a link ?


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