LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently March 29, 2024, 2:01 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 147 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8 ... 10  Next
Author Message
PostPosted: December 10, 2011, 2:11 am 
Offline

Joined: September 21, 2005, 6:09 pm
Posts: 265
Location: Laveen, AZ
Earley Motorsports wrote:
That looks better. Trial and error is how you do this. Keep at it.
:cheers:


Trial and error with PVC pipe for mockup might soften the blow to the pocketbook later ... just a suggestion.

-Steve

_________________
Mk Indy 7: http://locostusa.com/forums/viewtopic.php?f=35&t=9000


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 3:27 am 
Offline
User avatar

Joined: November 12, 2008, 6:29 am
Posts: 3567
kingkyle wrote:
The only cons I can think of right off the bat.

1. I believe its an iron block

2. The motor sits sideways so it uses a FWD trans, this is not a problem in the rear, but it causes a huge imbalance of weight. The motor and trans literally sit on top of the rear axles. It causes a 70/30 weight distribution or close to it. I'm trying for 60/40.


Obviously you're set and I'm not going to change your mind but this is a public forum and unfortunately when other people read this they may believe it as well, but it is wrong.

1. An engine is not automatically lighter because it is aluminium however many continue with this perception - as the old question goes, What's lighter, a Ton of feathers or a Ton of granite? If an engine weighs 400 lbs it weighs 400 lbs regardless of if it's made from titanium or if it's made from lead. Engines have to be chosen individually and their weights checked and not simply chosen for the material they are made from, a Chev 3.8 V6 all iron (block and heads) is lighter than an all aluminium Nissan V6 that is only 3.0 for example.

2. Being transverse or longitudinally mounted has nothing to do with weight distribution as they basically counter each other out as you turn them 90 degrees either way. You have one short mass or you have one long mass going forward and backwards.

In fact with the Subaru you have a shorter reach forward than others with a rather large gearbox hanging a long way out the rear past the axle line making you weight distribution worse.

Also note that with a transverse setup all the weight of the engine and gearbox is entirely forward of the rear axle line, something that all race car builders strive for so why don't race car builders use them .... longitudinally mounted have one huge advantage and that is for aerodynamics especially if you intend to run ground effect tunnels either side of the car. This sole reason is why all open wheeler racing cars have longitudinally mounted engines.

By the way, notice no one generally uses Subaru engines in open wheelers? Width is the biggest problem for the aeros mentioned because of the exhausts being exactly where your tunnels/diffuser should be but bet you don't believe the other reason - CoG too high. With a I4 dry sumped you can get the major mass of the engine very low down but the Subaru is always impeded by the exhausts and these are the very reasons Ferrari dumped boxer engines for F1 in the mid 1970's.

I know you have been to Pook's build thread, pictures there quite clearly demonstrate these points ..

Attachment:
pook 2.jpg

Attachment:
pook 1.jpg


I'm not against your build by any means, hope you go well but I will argue technical points.


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 11:07 am 
Offline

Joined: November 4, 2011, 7:22 am
Posts: 77
cheapracer wrote:
kingkyle wrote:
The only cons I can think of right off the bat.

1. I believe its an iron block

2. The motor sits sideways so it uses a FWD trans, this is not a problem in the rear, but it causes a huge imbalance of weight. The motor and trans literally sit on top of the rear axles. It causes a 70/30 weight distribution or close to it. I'm trying for 60/40.


Obviously you're set and I'm not going to change your mind but this is a public forum and unfortunately when other people read this they may believe it as well, but it is wrong.

1. An engine is not automatically lighter because it is aluminium however many continue with this perception - as the old question goes, What's lighter, a Ton of feathers or a Ton of granite? If an engine weighs 400 lbs it weighs 400 lbs regardless of if it's made from titanium or if it's made from lead. Engines have to be chosen individually and their weights checked and not simply chosen for the material they are made from, a Chev 3.8 V6 all iron (block and heads) is lighter than an all aluminium Nissan V6 that is only 3.0 for example.

2. Being transverse or longitudinally mounted has nothing to do with weight distribution as they basically counter each other out as you turn them 90 degrees either way. You have one short mass or you have one long mass going forward and backwards.

In fact with the Subaru you have a shorter reach forward than others with a rather large gearbox hanging a long way out the rear past the axle line making you weight distribution worse.

Also note that with a transverse setup all the weight of the engine and gearbox is entirely forward of the rear axle line, something that all race car builders strive for so why don't race car builders use them .... longitudinally mounted have one huge advantage and that is for aerodynamics especially if you intend to run ground effect tunnels either side of the car. This sole reason is why all open wheeler racing cars have longitudinally mounted engines.

By the way, notice no one generally uses Subaru engines in open wheelers? Width is the biggest problem for the aeros mentioned because of the exhausts being exactly where your tunnels/diffuser should be but bet you don't believe the other reason - CoG too high. With a I4 dry sumped you can get the major mass of the engine very low down but the Subaru is always impeded by the exhausts and these are the very reasons Ferrari dumped boxer engines for F1 in the mid 1970's.

I know you have been to Pook's build thread, pictures there quite clearly demonstrate these points ..

Attachment:
pook 2.jpg

Attachment:
pook 1.jpg



I'm not against your build by any means, hope you go well but I will argue technical points.



All great points cheapracer. This is exactly the reason i'm doing the build on this forum vs doing it with no outside help. Here is a pic that scares me. Its a race car replicas exo car with a Mitsubishi 4g63. Ive worked with these motors before. I've pulled then in and out of my evo and they are extremely top heavy.
Image

I do agree with you on the weight distribution. The I4 does sit about 8" front of the axles and with the extra long gearbox of the subi, they probably cancel out.

ALso very good point on the boxer exhaust isssue. I will have a flat bottom car and this does provide a problem. I'm going to research the SRT-4 engine a bit more to see what type of aftermarket support they have. I know they were raced in Speed World Challenge for many years and made around 300-350 hp pretty reliably. I would want to dry sump the motor to get the height down. I also need a fool proof shifting system. Cable shift makes a kit for the Subi and I think they make a retro fit kit for the 4g63.

You've got me thinking! thats a good thing :)


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 11:43 am 
Offline
User avatar

Joined: July 22, 2007, 10:58 pm
Posts: 388
Location: Zagreb, Croatia
ceapy's point about subaru COG is a valid one.. those engines sit high up when installed with their original boxes..

Image


My vote goes, of course, for an LS, but since you have decided against that... I will have to say SRT-4 looks interesting, but think about 4g63T also.. If you get a stock evo 9 engine you can have reliable 380 HP with no mods + you can use original ECU and with open ECU and tephra mods you can change engine maps as if you had a standalone.. as you had already discovered, cheapest HP is stock HP.. :)

_________________
Building a single seater middy BEC with GSXR 1000 power :)
build log: http://locostusa.com/forums/viewtopic.php?f=36&t=5899

day job: http://smg.photobucket.com/albums/v723/turbolimac/portfolio/


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 11:59 am 
Offline
User avatar

Joined: May 8, 2007, 9:50 am
Posts: 602
Location: Minnesota
That's a cool comparison picture of the boxer and drysump pushrod V8, can you make two more? One with the crankshafts at the same height, and one with the Boxer and a OHC wetsump I4?


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 12:07 pm 
Offline
User avatar

Joined: July 22, 2007, 10:58 pm
Posts: 388
Location: Zagreb, Croatia
that is not a dry sump V8.. :) but rather a normal 32 valve 4 cam northstar which is no example of a nice low V8, like an LS for example


as for the I4.. I'd need to find some pics.. Of course, the normal wet sump 4G will be higher than a subaru flat4, but it would be interesting to see and measure the actual COG of the engine, not just the pic.. Don't forget that in an engine, most of the weight is around the crank..

_________________
Building a single seater middy BEC with GSXR 1000 power :)
build log: http://locostusa.com/forums/viewtopic.php?f=36&t=5899

day job: http://smg.photobucket.com/albums/v723/turbolimac/portfolio/


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 12:11 pm 
Offline

Joined: November 4, 2011, 7:22 am
Posts: 77
kikiturbo wrote:
ceapy's point about subaru COG is a valid one.. those engines sit high up when installed with their original boxes..

Image


My vote goes, of course, for an LS, but since you have decided against that... I will have to say SRT-4 looks interesting, but think about 4g63T also.. If you get a stock evo 9 engine you can have reliable 380 HP with no mods + you can use original ECU and with open ECU and tephra mods you can change engine maps as if you had a standalone.. as you had already discovered, cheapest HP is stock HP.. :)



I really do want to do a LS6 but the transaxle puts me way over my budget. This is the fun part, trying to decide on a powerplant! Since I've had experience with the 4g63, I'd probably go with that over the SRT4. Although the SRT4 with more displacement will make more torque... I know the 4G63 has a HUGE aftermarket so thats appealing.


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 12:17 pm 
Offline
User avatar

Joined: May 8, 2007, 9:50 am
Posts: 602
Location: Minnesota
cheapracer wrote:
but bet you don't believe the other reason - CoG too high. With a I4 dry sumped you can get the major mass of the engine very low down but the Subaru is always impeded by the exhausts and these are the very reasons Ferrari dumped boxer engines for F1 in the mid 1970's.


I can't see the downward facing exhaust ports as being a real limitation to this kind of build, the sump/flwheel/transmission issues are much more significant for any of these proposed drivetrains. Designing an F1 car from scratch, sure, it's a consideration, but Porsche has had plenty of racing success in spite of it, albeit not in formula type cars.


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 12:22 pm 
Offline
Always Moore!
User avatar

Joined: November 9, 2007, 3:40 pm
Posts: 4074
Location: Pittsburgh, PA
Wouldn't the flywheel diameter ultimately determine the engine's minimum height and bellhousing size?

The 2.0 Duratec in my car has a chopped pan that is flush with the bottom of the bellhousing. There is about 1/8" of material on the bottom of the housing - if you milled it away the flywheel would be the next lowest point. Even with a dry sump there is no more room to be gained.

I'll pay more attention next oil change but I seem to remember the STI's drivetrain being similar.

_________________
-Andrew
Build Log
Youtube


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 12:44 pm 
Offline
User avatar

Joined: May 8, 2007, 9:50 am
Posts: 602
Location: Minnesota
kikiturbo wrote:
that is not a dry sump V8.. :) but rather a normal 32 valve 4 cam northstar which is no example of a nice low V8, like an LS for example


as for the I4.. I'd need to find some pics.. Of course, the normal wet sump 4G will be higher than a subaru flat4, but it would be interesting to see and measure the actual COG of the engine, not just the pic.. Don't forget that in an engine, most of the weight is around the crank..


Oops, guess I'm behind on my GM V8's :oops:

That' an impressively thin wet sump, does it also have a small diameter flywheel and low input shaft transmission to get the crank low to the ground in the car? From my previous experiments those always seem to be the limiting factors.

http://www.locostusa.com/forums/viewtopic.php?f=4&t=2306&start=15
I posted that in '07, there is now a bellhousing available for that combination from Bill Hincher.


Last edited by Glen on December 11, 2011, 12:49 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 12:46 pm 
Offline
User avatar

Joined: May 8, 2007, 9:50 am
Posts: 602
Location: Minnesota
a.moore wrote:
I seem to remember the STI's drivetrain being similar.



This is true, but the input shaft on the Subaru transmissions are relatively high (although maybe the new RWD one from the Toyobaru will be better :twisted: )


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 1:06 pm 
Offline
User avatar

Joined: November 12, 2008, 6:29 am
Posts: 3567
kingkyle wrote:
Here is a pic that scares me. Its a race car replicas exo car with a Mitsubishi 4g63.


The SLR is very low and one thing they haven't done there is roll the engine forward say 15 degrees, this effects both lowering of the engine's CoG, raises the driveshaft output for more horizontal driveshafts and moves your engine weight forward.

The engine bay on the SLR is too small I guess but yours is a scratch build so you can allow the room for it (any transverse motor I mean).

Surely the SRT4's driveline is cheap to buy there?


Top
 Profile  
Reply with quote  
PostPosted: December 11, 2011, 1:29 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7652
Location: Massachusetts
Quote:
Wouldn't the flywheel diameter ultimately determine the engine's minimum height and bellhousing size?


On my Formula Ford the flywheel is in fact the lowest part of the car. If you lower it too much the ring teeth hit the pavement. It's required to have a stock flywheel though.

Quote:
This is true, but the input shaft on the Subaru transmissions are relatively high


I think this is true of all the street transaxles. The input shaft is above the output shafts by about 3", a little less but not much. When used for racing with a dry sumped motor they are generally inverted. At least when used with non-boxer engines. That's why the VW bug and Porsche units are common, they will run upside down. I don't think that's the case with the Subaru and am unsure about the Audi units.

I think you're thinking high horsepower because you're used to heavy cars. Start with less and learn to drive it, you'll still be happy and it's not like people with street cars are going to be passing you at the race track.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
PostPosted: December 14, 2011, 1:40 pm 
Offline

Joined: November 4, 2011, 7:22 am
Posts: 77
Hey Guys,

I picked up some C6 corvette spindles and they have upper ball joints attached. If i'm going to be building a full spherical Heim suspension do I need to run ball joints? I dont care about vibaration. Its a dumb questions but I want to know if I need to run the upper ball joint. Pro's / cons?
Image
Thanks


Top
 Profile  
Reply with quote  
PostPosted: December 14, 2011, 2:37 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7652
Location: Massachusetts
As long as they are in fine shape, it's a good idea.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 147 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8 ... 10  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 33 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
POWERED_BY