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Barra XR8 - Built to rev but can't

10K views 21 replies 18 participants last post by  Cobra  
#1 ·
Are there any people out there with some technical knowledge about the new 5.4l Boss engine.
It seems that it has great torque and is designed to rev, however the mags are saying the long stroke prevents it being revved over 6000rpm without letting go.
Thus we have an engine that breathes very well but it can't rev any more than 6000rpm. It is something of a paradox.
So I suppose the question is, is there any room in the current block for increasing bore size and then being able to shorten the stroke to increase rev potential? If not, the holden unit will still have the wood on the XR8 and GT (even though it uses more oil than petrol).
This then would be a very bad thing.
Please respond
Stephen
 
#2 ·
The Mustang Cobra R 5.4 4V revved to 7000rpm with the aid of a forged steel crank and Carillo rods. Based on that there shouldn't be any reason why FPV can't engineer it to rev to 7000. To answer your question, yes it can be de-stroked but i'm not to sure about bore increases
 
#4 ·
I can honestly tell you that the Boss motors don't need to rev past 6000. They pull like a steam train from low down & by the time you hit 6000 in 2nd gear you're well & truely flying.
 
#5 ·
The only problem I find with mine is that I reach 6000 very very quickly. I wish I could go more before having to change gears at the second blink of an eye.

Alex
 
#6 ·
I have been told by a mechanic who has modified the Sohc 5.4 in a F series truck that it can be safely revved out to around 5600rpm+, so i would guess that the Boss has a little more in her but 6000 is a safety margin.
 
#7 ·
It's true, the 5.4 will never rev much past 6000rpm in street trim.
Even with some very strong (read expensive) internals, it is unlikely it will go past 6500rpm reliably.
It has to do with with it's undersquare bore/stroke ratio, it's very diesel like in it's config.
It would very likely throw conrods and/or split bores if revved beyond 6500rpm.
6000rpm is a safe limit for road use.

Have you ever heard of a high revving Ford I6?
It too has an undersquare config and won't rev for the same reasons.

Rick.
 
#9 ·
I think the journos are talking through their butt. It's like they talk about traits of certain IRS types, struts etc. I reckon if you put them in a car where they didn't know the tech stuff up front they'd be hard pressed to know what's going on. Like the Control Link on Holden IRS - in reality the difference is very small and hard to pick unless you know it's there.

Same thing for engines. The Ford Modular engines are at max bore size already and the engine was originally designed to run at 4.6 litres. Obviously Ford Oz decided the torque was important and went for the 5.4 crank. It still revs to 6k and seems to do the job.

There are so many more considerations than bore x stroke, however there are advantages and disadvantages for both. Like 2 valve versus 4 valve - the LS1 has much bigger bore so the flow of its larger two valves is obviously not that much less than the smaller valves of the Boss which are limited by the bore size (this engine would not be real happy with 2 valves for this reason.

All that matters is what happens when right foot meets plush pile carpet and the tacho starts arcing around - LS1 and Boss are both fantastic :hit:
 
#10 ·
Aussie Pete said:
All that matters is what happens when right foot meets plush pile carpet and the tacho starts arcing around - LS1 and Boss are both fantastic :hit:
Exactly Petey Boy.. The performance market in Oz has finally delivered some goodies from both sides of the spectrum. If people aren't happy with either a Boss or an LS1 then you will never please them. It's that simple..
 
#11 ·
Aussie Pete said:
I think the journos are talking through their butt. It's like they talk about traits of certain IRS types, struts etc. I reckon if you put them in a car where they didn't know the tech stuff up front they'd be hard pressed to know what's going on. Like the Control Link on Holden IRS - in reality the difference is very small and hard to pick unless you know it's there.
Not completely true. The first thing that blew me away about the Control Blade in the BA XR's was the ride quality. Compared to anything else, AU XR, VT/VX/VY SS, it's miles ahead. I wouldn't need to be told what car was what for this!
 
#12 ·
Mr Sparkle said:
Not completely true. The first thing that blew me away about the Control Blade in the BA XR's was the ride quality. Compared to anything else, AU XR, VT/VX/VY SS, it's miles ahead. I wouldn't need to be told what car was what for this!
Of course in addition to the gigantor BA kerb weights the weight of our two fat arses that day could have something to do with how well tied down the car felt :angel:

Cheers
Jason
 
#13 ·
Of course it also depends on your definition of 'quality' Sparkles.

If you're happy smoothing out the bumps but lolling around corners with body roll and lack of feel through the wheel then the BA XR is 'quality'.

If you don't mind the bumps but prefer to go fast through a corner with a wheel that communicates every detail without being harsh then the AU3XR8/T3 are 'miles ahead'.

I guess Ford will take time to make a better XR set-up just as they did with AU.

Of course the Commodore has sucked from day 1 and hasn't gotten any better. But of course we all know that straight line performance is more important.....
 
#14 ·
BammasAUIIIXR8 said:
Of course it also depends on your definition of 'quality' Sparkles.

If you're happy smoothing out the bumps but lolling around corners with body roll and lack of feel through the wheel then the BA XR is 'quality'.

If you don't mind the bumps but prefer to go fast through a corner with a wheel that communicates every detail without being harsh then the AU3XR8/T3 are 'miles ahead'.

I guess Ford will take time to make a better XR set-up just as they did with AU.

Of course the Commodore has sucked from day 1 and hasn't gotten any better. But of course we all know that straight line performance is more important.....
I hear what you're saying! My point though was that there is a definitive difference between the VY and BA in a lot of areas, and the growingly popular answer of "they're both so close it doesn't matter" is simply not true! They're plenty different!

As for the BA suspension, I'm sure it could be stiffened up a little with due compromise on ride quality, but for a first release of this new model Ford were no doubt going for the "Euro" level of ride/handling compromise, and consequently sprung it a little softer than the AU XR's. For mine, even with stiffer springing, the extra lard in the BA would generate body roll and give the impression of softer springing than it really has.

As for my current choice of suspension, check inside my wheel arches - SuperLow King springs and Koni adjustable shocks dialed to the stiffest setting! Easy to see how I was impressed with the ride/handling compromise in the BA isn't it :wiggle:
 
#15 ·
BammasAUIIIXR8 said:
Of course it also depends on your definition of 'quality' Sparkles.

If you're happy smoothing out the bumps but lolling around corners with body roll and lack of feel through the wheel then the BA XR is 'quality'.

If you don't mind the bumps but prefer to go fast through a corner with a wheel that communicates every detail without being harsh then the AU3XR8/T3 are 'miles ahead'.

I'm trying to figure out if we're talking about the same car here?

If there's one thing I will never complain about it's the amount of feel communicated through the wheel on the BA. My wheel works quite well at communicating every detail, and the suspension is less harsh under any circumstance than an AU thanks to the Control Blade rear end.

And unlike some (so it seems), my fat arse appreciates a supple ride that doesn't achieve a level of cornering ability by using shocks that shake the fillings out of your back teeth like any Commodore.

While I have the optional 18's with the 245/40 Dunlop SP9000's, I can't believe they'd make that much difference over the 235/45 SP3000's on the standard 17's...

And to use the Great Ocean Road as a well known example, I'd back a BA over the equivalent model AU ANY day of the week if you had two drivers of equal skills.
 
#16 ·
hmmm
I would too expect the BA to be Quicker over the Ocean Road
except for a T3 Au against an BA XR 8 Hard to say about the GT's yet
Have driven both the T3 and the XR8 , the T3 is so sure underfoot
Much more so than any other AU or BA I have driven
 
#17 ·
Everyone keeps on talking about Control blade and how it handles BUT you forget that it was not only designed for handling but also BRAKING!. When we where at the track last week you could feel the control blade pull the rear end down to the ground under extreme braking, it just settled the car before the corner in the rear, As you know that sometimes under extreme braking in a conventional car the rear will feel a little light on entry to a corner.

Elmer Fudd
 
#19 ·
FM said:
I can honestly tell you that the Boss motors don't need to rev past 6000. They pull like a steam train from low down & by the time you hit 6000 in 2nd gear you're well & truely flying.
Shyte yeah chucky, why have more rpm when you dont really need it? It pulls from down low enough as it is then at 4 grand it hits the real power....horn.

In terms of improvement? The bore may be undersquare but ask yourself the question- why would ford develop an engine that will only survive a couple of models? It has all the latest technologies and go-fast bits and is set for a long run and they have left themselves with some handy options for series 2 and thereafter....

They have aimed at being a thorough competitor with BA, and have achieved it. Now they have the product to move foreward. :evilking:
 
#20 ·
For a big V8 anything over 5.0L the current rev range of 6000rpm is very good going given the under square nature. I have no doubt that Ford will stretch the rev limit with an increase in power for the future. I think 6200-6300rpm is more than possible. Though i don't see the need to go over 6500rpm.

Perhaps the 220kw 5.4L 3 valver seems to be abit rev lacking, but no doubt Ford will sort that out in the comming models.

From the seat of my pants i can say that the Boss engine has a LS1 where theres a distinct band from 3000rpm onwards.
 
#21 ·
Reading in Motor, they commented how the BOSS motor pulls all the way, whereas the LS1 dosnt do much till almost 4000rpm, then comes on with a big bang.
I suppose this would make the LS1 feel quicker, as a seat in the pants feel, because all of a sudden you have power. The Boss just has so much pull from low down, therefore, dosnt feel as quick.
 
#22 ·
Mr Sparkle said:
I hear what you're saying! My point though was that there is a definitive difference between the VY and BA in a lot of areas, and the growingly popular answer of "they're both so close it doesn't matter" is simply not true! They're plenty different!

As for the BA suspension, I'm sure it could be stiffened up a little with due compromise on ride quality, but for a first release of this new model Ford were no doubt going for the "Euro" level of ride/handling compromise, and consequently sprung it a little softer than the AU XR's. For mine, even with stiffer springing, the extra lard in the BA would generate body roll and give the impression of softer springing than it really has.

As for my current choice of suspension, check inside my wheel arches - SuperLow King springs and Koni adjustable shocks dialed to the stiffest setting! Easy to see how I was impressed with the ride/handling compromise in the BA isn't it :wiggle:
I was told that Superlows were not even rated for street use because how low they are. My mates only got King Spring Lows on his EA and he still bottoms out alot and has scraped the chassis many times.

I will go King Spring lows after i put new wheels on my XR6.