RS4 600BHP from Digi-tec

[Bushy]

this is getting more and more interesting

I also read that the engine gets rebuilt in the upgrade with some internal components being uprated

[Andiroo]

Hi mate, how you keeping?

Seems to be all boost and no thought to me, what do you think?

Andiroo

[Bushy]

yep

but they do seem to do a good engineering job on it

i reckon we should go for ducting over the front arch and exit out like a BMW M3

That way you would get a nice air flow through the intercooler, more downforce at the front and no heat onto the brakes

ANy comments?

[Andiroo]

Initially sounds a good idea doesn't it? Spoke with Sportec back in the summer months - unfortunately that type of proces takes the airflow away from above the venturi on the undertray and as a result the hot air in the engine bay doesnt get sucked out efficiently - cause more problems.

Hopefully while Scott is away in sunny Oz he will come up with somethin for us. At the mo it's just charge cooling with water I'm afraid

Andiroo

[Bushy]

but surely it wont effect the venturi, as you have ducted air onto the IC, then it vents out by the wheel
so if you duct it out, behind the wheel the venuri won't change


or am i talking my usual bollox?

[Andiroo]

Thats what I thought but unfortunately the airflow goes three ways - side duct, wheel arch louvres (pointless), and back over the undertray towards the rear. Supposedly the highest airflow rate (path of least resistance) is the latter (beleive it or not!)

In trackday mode, with only slight high speed runs, it's supposedly better to run without the tray - wouldn't like to try it though

Andiroo

[rs4steve]

internal works; lower compression ratio more boost less detonation working (on experience)

example;(standard engine 205bhp 10psi)
1) sierra cosworth standard comp 8.0 to 1 can run boost pressures on standard injectors standard intercooler can run max boost 14psi(270bhp)
2) same spec bigger intercooler bigger injectors max boost 23psi(330bhp)
3) lower compression(7.2 to 1) lightened balanced bottom end bigger intercooler uprated hybrid turbo even larger injectors max boost 28psi(440bhp)

could run even higher levels of boost if a 8 injector setup was used then you would get anything upto 550bhp dependent on camshafts

the heat is not as intense due to compression ratio lowered to a certain degree to allow higher levels of boost with no detonation problem

must take into account; being lower comp lower pickup plus lower bottom end ,torque suffers,fuel consumption,competition paddle clutch required difficulty pulling away

hope this helps steve

[toasty]

I tend to agree, I can't see where all the extra heat goes...

Take a standard RS4, 380bhp at which level it is very comfortable.

If you up it to (say) 600bhp, then thats an extra 220bhp in terms of engine power.

But if you consider that the average internal combustion engine is only (say) 40% efficient, then the extra 220bhp (or 166kw) is producing 250kw of heat!!

(I'm assuming that the RS4 can deal with the heat that results from the standard 380bhp, but needs help with at least some of the 'extra')

This is an awful lot of heat, put into perspective the average house boiler is around 100,000 btu which equates to only 28.5kw !!

So how to get rid of this heat? (and this is really the point of my post)

People often talk of water misting, I was curious to see what effect this could have:

Take 5 litres of water at say 20 degrees C.
The most energy this could absorb (i.e remove from the engine bay) would be if we vaporised it (turned it into steam) and I doubt misting the intercoolers would be quite so efficient

This does take a lot of energy:
First we'd have to heat it to 100 degrees
Specific heat capacity of water is 4.2Kj/kg so an 80 degree increase of 5 litres would require 80*5*4.2Kj=1.68Mj

Secondly we'd have to turn it all into steam:
Specific Latent Heat of Vaporisation of water is 2.23Mj/Kg so to turn 5kg (1 litre of water weighs 1kg) of water into steam would take 2.23*5=11.15Mj of heat

Giving a total of 12.83Mj

Remember we are trying to disapate the extra 250kws of heat by vaporising this water, so the question is, how long would the water last.

Answer:
52 seconds!

I guess you wouldn't have to dissapate all the extra heat, as I suppose the engine can take more than 380bhp (Plenty of tuned ones around this forum that seem ok)

Certainly for trackdays (race times of about 5 minutes) it would seem that water misting would be able to support an extra 40bhp with no increase in underbonnet temperature.
(40 bhp would result in about 45kws of heat, which would take 4.8 minutes to get through 5litres of water)

I'd be interested to know what affect water misting has in the real world, to see if my calculations have any relevance! [img]images/graemlins/grin.gif[/img]

[Andiroo]

Good points Steve/Toasty,

After we spoke at Anglessey Steve, I looked into the Motronic multi point injectors with ECU etc. Seems like a very good way on controlling and getting more power. Front end seems rather complex, but not a massive hurdle.

The lowering of the compression ratio initially was deemed a good idea, until we looked into the characteristics of the camshafts, both the intake and exhaust profile. It looks like we could indeed lower the compression ratio and raise the boost to well over 2bar with the modded turbos, manifolds etc, but the power band of 550bhp (easy) would be between 4200rpm and 6000rpm !! Reckon that sort of gusto would be a bit much for the OEM drivetrain even with a paddle clutch [img]images/graemlins/frown.gif[/img]

The compromise seems to be the combining of an S4 torque curve and the RS4 torque curve ie peak high and early, but sustain for at least 4500rpm. This is what we are going for. The rebuilt K4 turbos will flow 286bhp each, so all we need to do is make sure the intake, exhaust manifold and cylinder heads dont restrict too much. By keeping the smaller turbos, the target of 4500rpm power range is still achievable.

If we take what Toasty has explained very well indeed, then yes, water can indeed help. Not only will it limit detonation, but it will also increase bhp within the turbos capabilities ie. give us more chance of reaching the 572bhp max.

The water injection or charge cooling system is introduced after the intercoolers, but well before the inlet plenum. It is however, only triggered by three combined inputs, over a mappable ecu. These inputs are boost, intercooler housing temp and inrtercooler intake air temp. Only when these three combined reach your mappable peaks does the air get charged (the length of the charge is also dictated by all three). This way you're not sat at the lights with a hot car, getting hotter, with water pissing into your intercooler pipes triggered by only one or two inputs. The three input method of charge cooling is known as using the "Fang Factor", and we reckon this, coupled with the Sportec intercoolers and the Carbon Dynamics Airbox should give us a good chance at nearing the 550bhp mark, with no driveability or heatsoak problems on trackdays. Only time will tell [img]images/graemlins/wink.gif[/img]

Under bonnet temps are another issue we are looking at. The standard radiator shroud flaps for airbox on the left and general cooling on the right are deemed to be piss poor for the job. Any ideas guys????

The fix for the airbox seems to be losing a headlight as per S4 Blitzkrieg, and modifying the front number plate housing for general cooling.

My personal thoughts are a carbon fibre bonnet with a cleverly designed ramair setup to cover both issues. Tastefully done of course [img]images/graemlins/tongue.gif[/img] [img]images/graemlins/tongue.gif[/img] [img]images/graemlins/tongue.gif[/img] [img]images/graemlins/tongue.gif[/img]

Once these issue are sorted, and more importantly the RS6 Saloon arrives, then the interior's coming out. Sportec do some lovely seats and those OEM ones weigh a ton. Probably need to keep something in the back as the dogs wouldn't appreciate being in the boot of an RS6 [img]images/graemlins/cool.gif[/img]

Andiroo

[Bushy]

Strewth [img]images/graemlins/shocked.gif[/img]

Right if you are thinking of using NOS could you not use this to get more power at lower revs then lower the compression ratio as discussed above?

If i understand correctly you lower the compression and increase boost, eas to get more power just a limited range, then use NOS to get the thing moving

Or am i talking rubish AGAIN [img]images/graemlins/grin.gif[/img]

[Andiroo]

You are partly right mate [img]images/graemlins/wink.gif[/img] see response to JR's post

Andiroo

[bettonracing]

My $0.02
Drag car?
Large turbo. lo-rpm N2O as per 'Bushy'. Dry Ice intercooler. gear ratios to keep u on boost.

Circuit car?
Large turbo. Water/Meth inj. gears to keep u on boost. Anti lag program. Driving alterations.

Rally car?
Large turbo (per specs. appropriate for restr plate & torque). water inj. water spray (to wash off dirt!). anitlag program.

(starting to see the trend?...)


Street car?
See Circuit car or Rally car. [img]images/graemlins/FIREdevil.gif[/img]

[Crafty]

Interesting post.

Surely the answer to reducing under bonnet temps will be vents in the bonnet, although this may ruin any "stealth" aspect of the car. the carbon bonnet could obviously be made with these built in.

Far as lowering CR goes.. very common on big power turbo engines (esp. cossies as steve says), but, take a look at WRC ( and older rally cars ) if you will, CR Ratios of 9:1 are common.. I have a book at home that details specs of rally cars, I'll post some when I can.

I think looking at what skyline/supra boys do is a good idea.

far as using Nitrous goes.. yeah why not, but use it for cooling rather than a "power gain", its very very cold out of the bottle and could be used to significantly reduce the inlet temps with only a modest squirt. The duration etc could be controlled by a mappable ecu..

Why ECu are you using Andiroo ? motec ?

[Andiroo]

Hey Crafty, will still be running the Motronic for the next few months. The development will then take it the Motec route as I fully agree this is the way to go for maximum power and flexibility [img]images/graemlins/laugh.gif[/img]

The reason for the delay in going straight to Motec is that it supposedly has a complicated "front end", and I didnt want any initial delays. AmD are fully conversant with the Motronic, although admittedly the Motec is the ultimate route to go - we will have to wait and see.

Andiroo

[Riz_RS4]

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