V6, Inline 6 or Inline 5??

[KFC]

I don't have the chassis yet as I might need to make changes to the chassis before it's built.

I'm trying to decide on what engine to fit to the "haynes" chassis.

V6? BMW 2.5L or 3.0L or the Fiat coupe inline 5 20v engine?

Obviously it would be much easier to fit the MX5 running gear, engine and gearbox. I just thought if I'm going to build it then do it with style, twin exhaust with that lovely sound of a V6. :D

I thought the duratec V6 would fit better than a M52 BMW engine, both with standard gearboxes fitted to their engines but the Duratec seems quite heavy, 200kg? Upset the handling too much? :confused:

Any thoughts on the complications of mix matching gearboxes and rear gearbox with diff out of 2000 Audi A6 to try and balance the car better or is it just not worth the agro?

Thanks in advance

Kev

[Davey]

"In my humble opinion, big heavy blocks arent ideally suited to a lightweight sportscar, generally youll see a lot of understeer and a bit too much torque at the back. Thats just my opinion though so dont take it too seriously."

A heavy motor isn't ideal for a lightweight sports car I agree but it doesn't necessarily upset the handling and doesn't necessarily give understeer. If it is mounted further back in the engine bay to centralise its mass then it shouldn't give any more understeer than a Zetec would.

"too much torque at the back" I don't understand what you're saying here. Do you mean it would give too much torque at the wheels being a bigger engine with more torque produced lower in the rev range or are you suggesting the torque reaction might twist the chassis?

Having been in the motor and related industries for 35 years I was brought up on the principle of TTW, Torque Turns Wheels. Personally I'd rather have a bigger motor giving a wide spread of torque across the range over a small capacity revvy lump with little torque at the bottom end and then a sudden surge higher up the rev range. Each to their own of course but with a better spread of torque you don't always need to be changing gear to keep it in the "power band".

It also depends on what you intend to do with the car, if its intended as a quick and fun roadcar, as mine is planned to be, then the bigger lump will give more relaxed driving. If you intend to use it mostly at track days or even as a full on race car, whether for hillclimbing/sprinting or circuit racing then the smaller capacity, lighter weight peaky engine may well be a better option.

Just my thoughts,
D.

[robo]

There is no "better" engine, I can understand someone building a 1ltr roadster the same as I do a 3ltr. I prefer the bigger lazy unfussed lumps but thats just me. Its no different than a bike really, you see kids laying flat on their tanks with bikes at 40mph screaming the nuts out of them, big bike comes past at little over tickover at the same speed [no noise]. Same job different approach both riders are happy.
The engine weight thing is a non issue within reason as some of the four pot engines are as heavy as the sixes and eights, the difference is less than a good dump after a curry night..

1.3 13B TT (FD) Alone
+ Five Speed

CA18DET with trans 389lb

SR20DET Complete
+ Five Speed 490lbs (source Sport Compact Car)

Datsun L6 Alone
+ Four Speed

toyota 1UZ-FE + R154 mission 486lbs
+ W58 mission 466lbs

RB25DET Alone
+ Five Speed 700 lb complete

RB26DETT Alone
+ Six Speed

L28 complete with stock manifolds, SU's, and A/C compressor + 5 spd 523lbs

7MGTE complete with turbo and A/C compressor 515 lb
w/ R154(125lbs alone) 640lb

2JZ-GTE Alone 594 lbs
+ Getrag Six Speed 746lbs

VH45 508 lbs

LS1 Alone
+ T56 Six Speed

Chevy L98 Alone 540 lbs with iron heads, 510 lbs with aluminum heads
+ 4+3 OD

Chevy LS1
459(automatic)
503(manual)

LT1/LT4
562 (automatic)
620 (manual)

LT1/LT4 Alone
562 (automatic)
620 (manual) ZF Six Speed

Chevy SB (All Iron) Alone 575 lbs
+ T56 Six Speed

Chevy SB (iron + Aluminum) 500 lbs
+ T56 Six Speed

Ford SB (All Iron) Alone 550 lbs ?
+ T56 Six Speed

Ford SB (iron + Aluminum) Alone 470 lbs?
+ T56 Six Speed

Chevy BB (All Iron) 685 lbs
+ T56 Six Speed

Chevy BB (iron + Aluminum) Alone 590 lbs
+ T56 Six Speed

Viper 8.0 L alone 716 lbs
+ T56 Six Speed

Viper 8.2 L alone 716 lbs?
+ T56 Six Speed

Bob

Guilty of going V8

[wylliezx9r]

My argument is, that these cars need very little torque. My car will trundle around @ 30 mph in 6 th gear easy, I proved it to a guy at a show the other week and he couldn't believe it. And will do 60 in under 5 secs and has enough power for power over steer when it takes your fancy.
I guess as others have said though, ultimately its what you wnt from the car, tourer, track car, mix of the both. But in my opinion lighter must be better :p

[robo]

http://westfield-world.com/power-to-weight.html

Have a fiddle with the above, just love power:) The weight difference of a light four pot to a medium weight 6 pot is about 5% on a total build which is more than enough for the bigger engine to cope with.

Bob

[shh120m]

"In my humble opinion, big heavy blocks arent ideally suited to a lightweight sportscar, generally youll see a lot of understeer and a bit too much torque at the back. Thats just my opinion though so dont take it too seriously."

A heavy motor isn't ideal for a lightweight sports car I agree but it doesn't necessarily upset the handling and doesn't necessarily give understeer. If it is mounted further back in the engine bay to centralise its mass then it shouldn't give any more understeer than a Zetec would.

"too much torque at the back" I don't understand what you're saying here. Do you mean it would give too much torque at the wheels being a bigger engine with more torque produced lower in the rev range or are you suggesting the torque reaction might twist the chassis?

Having been in the motor and related industries for 35 years I was brought up on the principle of TTW, Torque Turns Wheels. Personally I'd rather have a bigger motor giving a wide spread of torque across the range over a small capacity revvy lump with little torque at the bottom end and then a sudden surge higher up the rev range. Each to their own of course but with a better spread of torque you don't always need to be changing gear to keep it in the "power band".

It also depends on what you intend to do with the car, if its intended as a quick and fun roadcar, as mine is planned to be, then the bigger lump will give more relaxed driving. If you intend to use it mostly at track days or even as a full on race car, whether for hillclimbing/sprinting or circuit racing then the smaller capacity, lighter weight peaky engine may well be a better option.

Just my thoughts,
D.


Im not too sure i would want to point your car into a corner, it looks rather heavy, and the chassis steel looks rather "pitted", especially the rails where the rear shock mount is fitted. I think your misguided on your torque principle, however you may need alot to move your barge of a car

Just my opinion


Nathan

[robo]

Not all the cars are being built to race round coke cans in a car park:D

Bob

[michael92]

I dont think there will be any problems :) I have a vauxhall v6 and omega box, and ive mounted mine as far back as possible! the only downside is.... I have to buy 2 cat converters :( expensive!!

[Davey]

Im not too sure i would want to point your car into a corner, it looks rather heavy, and the chassis steel looks rather "pitted", especially the rails where the rear shock mount is fitted. I think your misguided on your torque principle, however you may need alot to move your barge of a car

Just my opinion


Nathan

Can you not express your opinion without resorting to insulting words? BARGE? Really?
Yes it is going to be heavier than many other Haynes builds but as I said I'm building it for a quick road car not a circuit racer or hillclimber/sprinter. Having said it will be heavier it will still only be 750KGs ish, with C225BHP and a likely torque output of 200 ft/lbs plus it will still outpace most hot hatches and with pretty equally balanced weight distribution fornt to rear it should handle OK!

The steel may look pitted but as it is 3.2mm wall thickness there is no serious loss of strength, in fact it will almost certainly have more torsional rigidity than the standard book spec car.

I'm mistaken am I? TTW pal, TTW!

D.

[robo]

If yours is a barge mine must be the Titanic:eek: TTW is bang on , as the yanks say "there aint no replacement for displacement":)

Bob

[Davey]

If yours is a barge mine must be the Titanic:eek: TTW is bang on , as the yanks say "there aint no replacement for displacement":)

Bob

Cheers Rob, have you seen the youtube video of Kyle Dunkles 8000 lb Peterbuilt running a low 14 second quarter? Oh yes, he smoked a 240 BHP 2000lb Mustang at the time. Pete was giving 1000BHP but most important was the 3000+ ft/lbs of TORQUE! 8 wheels driving and he did mega burnouts, that's TORQUE for you!

When you tighten a whel nut up you do so to a given TORQUE figure, 100N/m for example. This equates to a FORCE of 100 Newtons being applied perpendicular to the radius from the centre of the turning circle at a distance of 1 metre from that centre. How much power is exerted?

Power is a measure of work done, or the ability to do work in a given time. BHP figures are a mathematical result of torque produced multiplied by engine speed and usually divided by a constant.

200ft/lbs of torque at 2K rpm will be more use in a road car than 1000BHP at 18K rpm and will accelerate that same car much quicker.

D.

[flyerncle]

Wouldn't go round corners too quick would it !
If you have ever driven an artic unit on its own in the wet you will understand.

[Davey]

Wouldn't go round corners too quick would it !
If you have ever driven an artic unit on its own in the wet you will understand.

Fair comment but I think this is splitting into two different debates. Which is better good torque from low down and spread over a wide rpm range or high revving peaky motor giving high peak BHP figures but little torque till its revving its nuts out is one subject, (as I said in my original reply a lot depends on what you intend to do with the car) the effect of a heavy engine on handling is another.

Having said that a heavy motor doesn't necessarily mean understeer if its placed well back in the engine bay (my original point). Point taken about driving a tractor unit on its own in the wet, been there played that game, fun it isn't. But have you ever seen truck racing? Those boys corner at speeds you'd think impossible in rigs weighing in at 7 Tonnes plus. Yes if a heavy motor is placed up front over the front axle for example a la Audi then understeer is almost guaranteed but move that weight back in the chassis to get as near to 50/50 weight distribution and any understeer will be caused by the steering/suspension geometry not the weight.

hopefully I've cleared up my points now?

D.

[flyerncle]

Clear as Dave, and points taken and agreed especially about understeer and VAG products (I have two 90 Quattros and they are a handfull in the wrong hands in the wet as I found out)getting the balance will be the making of a car,the one I built for Teamtrain has a lot of oversteer and the engine and rad etc are as far back as poss.

Friend of mine in California has a Chrysler 300 whatever in an estate version with a Hemi fitted to it SRT and upgraded box etc etc etc and it is quicker than many bikes from a standing start all down to torque,but it does weigh as much as a small house.

[phil clegg]

my haynes has a mildly tuned alfa v6 3.0,so i feel able to coment,there is ample power so much that the low gears wheelspin makes it difficult to use,at santa pod my best quarter i set of in third to avoid wheelspin,it has been properly cornerweighted and has good even weight distribution total weight 690 kg,i think it has a bit to much power .i thought i needed 200 bhp (too much)and this was much cheaper than trying to tune /install duratec,if i was building another i would go for a zetec with suitable mods about 165 bhp,or even bike power.It still sounds nice with pipes each side,one more point these are made for ourselves and any choice is good if thats what you want...

[raceral]

In my case I went with a 60 degree V6, that fit very nicely.
I am not sure if the engine is available over there, but it is a GM 3.4L.
It weighs very close to the Miata motor and produces around 200 hp in the trim I have it in.

Al

http://inlinethumb19.webshots.com/50130/2152572520000773316S600x600Q85.jpg (http://rides.webshots.com/photo/2152572520000773316CGjFXW)

[robo]

Yep too much power cant be used, understeer,oversteer and horrendous wheelspin , totally undriveable. Its all a load of Bull just build and enjoy , all problems can be sorted when finished.

http://www.youtube.com/watch?v=6oRamlkyS34&feature=related

And he`s not even giving it the beans.

Bob

[raceral]

I think too many people focus on horsepower and don't focus on the rest of the suspension and components that will make the 200 horsepower work.
Build the whole car to support 200 horsepower or whatever power you want, don't just throw a 2 or 300 hp engine in a 145 horsepower chassis and then expect to have a car that hookups when you dump the clutch.

When I built my chassis I built it to take the power of a small V8 if I should ever wish to install one later.
As time goes on though I find the 200 or so I have is just the right amount for what I use the car for, it works for me, but doesn't mean it works for anyone else.

Like Bob mentioned, build the car the way you want and enjoy it, the power is irrelevant, having a good time is relevant.



Al

[Big Vern]

To quote Colin Chapman, on whose lotus 7 our cars attempt to emulate, for increased speed just add lightness.
The lighter it is the better it will handle which means it should go round corners as well as just going quick in a straight line. A 100hp car that weighs half a tonne will be quicker than a 200hp car that weighs a tonne.

Nose heavy cars don't handle - Fact!

It's about power to weight not outright power. If you've power you can't use then its wasted.
My GTM libra has a 160vvc K series engine and to be honest it has too much torque and is not nearly as much fun to drive as my old MX5 was.
The caterham that went round the top gear track is nearly the fastest car they ever had there but by no means the most powerful!

[motomaniac]

. A 100hp car that weighs half a tonne will be quicker than a 200hp car that weighs a tonne.


surely the two cars would be the same, as they would have an identical power to weight ratio?????

[wylliezx9r]

surely the two cars would be the same, as they would have an identical power to weight ratio?????

In a straight line maybe but the lighter car would handle better !

[robo]

The caterhams dont own many of the circuits in this country, yes they are quick but a quick reccy of lap times will show that the nose heavy cobras and things like the nose heavy fancy new corvette stuff them good and proper on many tracks. That shite on top gear is hardly a bench mark, things like the veyron would eat the caterham on many circuits but is not at home in a slalom. If you took a caterham to lemans it would probably need another day on the track to complete the same race distance.
I did put a calculator across the subject and even the lumpiest engine you could put in a roadster only increases the total build weight by 5% so It wont bother me.:D If I lost a few stone it would make more difference.

Bob