3 litre 944 Turbo on track

[barks944]

I don't understand the benefit of that. You would seem to be reducing the compression ratio by basically decreasing fill rate of the engine. Arent you just pushing out what the supercharger has worked to push in?

 

[944Turbo]

Is the Hartech car running standard wastegate and boost control? If it is then there is potential for more

Having achieved healthy torque (approx 365ftlbs) with a good 2.5 on a standard turbo / intake /exhaust - mods were DPW/EBC/Chips/FPR/injectors/ a tweak to the air flow meter/ 1.2ish bar

http://www.cannell.co.uk/UKL%20F835VJT.htm

Tony

 

[Diver944]

ORIGINAL: 944Turbo

Is the Hartech car running standard wastegate and boost control?

Yes it is standard with a few shims, but I did notice that it was able to keep the 0.8 bar boost (on the dash gauge) up to the redline, whereas we all know that a standard 2.5 will gradually dip down to circa 0.6 bar by design. I am wondering if there is so much exhaust gas from the extra displacement that the wastegate doesn't vent it off quick enough, thereby holding the boost longer.

I have experimented with the electronic boost control on my 3.2L to try and delay the onset of boost and reduce lowdown torque and then get it to rise to the desired level as the revs increase. Unfortunately all I was able to do was gradually raise the boost further up the rev range wich still gives it a very large 480ftlb torque at 3500rpm. I think it's a lack of functionaility on the Greddy EBC as well as the back pressure from the standard exhaust yielding torque. The larger 3" exhaust will hopefully move the torque curve further up the rev range.

 

[TTM]

Since we are talking boost control, just thought I would mention that I have been getting pretty good "butt" results with the one supplied with the Vitesse set up.
I have set a relatively smooth boost ramp in order to avoid boost spikes and I see peak boost of 15psi at 3100rpm in 3rd & 4th gear, which is also what I saw with the black knob, but torque delivery feels both more civilised and quicker than with the black knob.

 

[DivineE]

ORIGINAL: Diver944

Yes it is standard with a few shims, but I did notice that it was able to keep the 0.8 bar boost (on the dash gauge) up to the redline, whereas we all know that a standard 2.5 will gradually dip down to circa 0.6 bar by design. I am wondering if there is so much exhaust gas from the extra displacement that the wastegate doesn't vent it off quick enough, thereby holding the boost longer.

My standard turbo always used to show it was holding 0.8bar to the redline, I think the standard guage is designed to be slow reacting to flatter the car and avoid showing that they all drop off.

 

[edh]

Mine held 11psi with the standard (but rebuilt wastegate) - I would expect the 26/6 cars to drop lower.

 

[DivineE]

ORIGINAL: sawood12

ORIGINAL: DivineE

Surely as a turbo has the ability to lift C/R a much simpler solution to altering the stroke of the engine (and all the complications relating to that) would be to have a C/R somewhere between that of a regular turbo and N/A engine and use a sequential turbo setup controlled electronically to give a boost curve exactly opposite to the engines natural torque curve.

Yes, this has an effect to a point, but is only a half-way house when used on it's own. This will determine what force is produced onto the crown of the piston due to expanding gases, but how you use that force depends on the mechanics of the moving parts of the engine. For example, if you have a constant force but increase the radius arm it acts on, the torque is increased at the pivot - so same force acting over a longer distance and more torque.

Surely you could adjust the boost in this way to improve any engines natural characteristics be it natuarally high in torque or hp? Maybe my understanding is worse than I thought? Not being sarcastic, genuinely curoius as to what I might be missing in my understanding of compression pressure. I understand that if the same pressure acts on a longer stroke, long crank throw more of its energy will be converted into torque but the rate of twist will be slow, I understand that on a short stroke, small crank throw less energy will be used to turn the same rotation but it will turn faster so higher bhp but less torque. Are you saying that the piston applies less pressure on the gasses in a short stroke engine so the compression of the gas is lower? Or maybe the higher the RPM, the higher the C/R because the gasses are compressed faster so get hotter due to friction?

How does it change if you are able to get the same amount of fuel and air into the cylinder at all RPM's? - in theory

 

[DivineE]

In ideal world I meant something like this. Where the boost pressure of the turbo ballances the torque to control C/R and give a much flatter torque curve as a result (not shown)

 

[Barry Hart]

Interesting discussions going on between some of you - of course our engine has more potential - we specifically just wanted to see how it would perform in absolutely standard 944 turbo spec just with a bigger capacity (bigger injectors as they are neccessary to deliver enough fuel at higher revs) as we thought it would achieve an objective we set for a nicer road car - it was never even expected to be suitable as a track car and we only tried it at Oulton because it was getting a bit dangerous on the roads around Bolton and we thought it made sense to be somewhere safer with people that are familiar with the circuit and cars.

It was also interesting to see how a very under developed but torquey engine would perform in a track situation - given my obsession with the shape of the torque curve within the rev range the gearbox forces you to use rather than the highest bhp figure to brag about.

Our next engine will explore the other top end of the range and be more relevant to your recent discussions.

I do not have time unfortunately to get too involved in some of the discussions about crankshaft throws etc but it is obviously a good idea to have a variable control to the boost or waste gate or by a dual waste gate as a way of influencing the compression pressures at different revs and conditions - it is just that in my limited experience - if you have a big turbo, pipes and peak boost pressure there is still a lag in repsonse that I prefer to try and avoid - perhaps time will prove me wrong on this and it is one of the things we want to test. We will be trying to get the best torque curve we can with the next engine but the third engine we build will be the one we will try and combine the benefits of both of the earlier ones at each end of the scale.

It is a relativley short stroke engine anyway (104 * 88) and anything that alters the stroke also alters the capacity of course - so difficult to compare like for like.

Baz

 

[TTM]

I have a (stupid?) question regarding the impact of the rod/stroke ratio.

We know that the lower the rod/stroke ratio, the higher the lateral load on pistons/cylinders.

Under full load, as the lateral load on cylinders will be higher on a turbocharged engine than on its NA counterpart, is the turbo engine likely to wear its bores more quickly than the NA engine?
Could that be the reason why Porsche chose Nikasil over Alusil when they built the 968 turbo S?

 

[barks944]

ORIGINAL: Diver944

ORIGINAL: 944Turbo

Is the Hartech car running standard wastegate and boost control?

Yes it is standard with a few shims, but I did notice that it was able to keep the 0.8 bar boost (on the dash gauge) up to the redline, whereas we all know that a standard 2.5 will gradually dip down to circa 0.6 bar by design. I am wondering if there is so much exhaust gas from the extra displacement that the wastegate doesn't vent it off quick enough, thereby holding the boost longer.

I have experimented with the electronic boost control on my 3.2L to try and delay the onset of boost and reduce lowdown torque and then get it to rise to the desired level as the revs increase. Unfortunately all I was able to do was gradually raise the boost further up the rev range wich still gives it a very large 480ftlb torque at 3500rpm. I think it's a lack of functionaility on the Greddy EBC as well as the back pressure from the standard exhaust yielding torque. The larger 3" exhaust will hopefully move the torque curve further up the rev range.

If you are using a standard DPW setup I don't think you can open the wastegate any earilier than the natural boost curve allows. You can only put opposing pressure on the wastegate diaphragm to keep the wastegate closed for longer making boost rise quicker. To slow down the onset of boost you would need to have a pressure source indpendent of boost pressure to drive the wastegate open.

 

[Diver944]

Wow I can't believe it's been nearly 4 months since this track day, but today I finally sat down and uploaded some of the incar video on to Youtube. I only had 5 flying laps to work with so I picked the quickest one with the least traffic, but unfortunatley Stuart and I were having a bit of a chin wag, so apologies for the commentary [&:]

http://www.youtube.com/watch?v=wKuVWfM6wr4

 

[333pg333]

Actually very reminiscent of video with LIL Paul. I recognise your smooth driving but also the torquey engine characteristics.
Looks a great road car too.

 

[Diver944]

Ah - not me driving on this occasion, I was merely ballast while Stuart showed me the way round

 

[Big Dave]

Paul
Nice little vid.
Pity you had the wrong "guide" with you....[8|][8|][8|][8|]
The line through druids... Well it beggars belief.
And it wasnt just because you had the VX 200 in front, thats his line all the time,,,, SO wrong....[8|][8|][8|][8|][8|]
Thats THE most important corner on the circuit....[][][][]

 

[edh]

Bit harsh Dave - they were only cruising round (why not show us one of your vids & we can see how it's really done? )

Actually I used that line a couple of times last Wednesday when I outbraked myself in the Honda [] - at least you get a good (safe) line into the second apex that way []

 

[944 man]

Boasting about driving prowess is foolish, because theres always someone better.

 

[Neil Haughey]

ORIGINAL: edh

Bit harsh Dave - they were only cruising round    (why not show us one of your vids & we can see how it's really done? )

I was going to say the same thing, cruising through the bends like that is loosing an easy 5 or 6 seconds compared to a maximum attack lap. Slightly off line on one bend perhaps a couple of tenths? I would definitely feel safe and comfortable in that car with Stu its pretty clear he was driving way within his and the cars envelope.

Its an interesting point of debate though, if one does an analysis based on car performance, racing lines, driving the traction circle etc. it quickly becomes clear that many place waaay too much stock in this belief of the perfect racing line.
Here is a linky worth digesting;
http://www.mitchellsoftware.com/Driving%20Simulator.htm

 

[Big Dave]

Ed.
The problem with using that line through Druids.
Is you go that deep into the first corner your actually running on marbles, So when you then try to turn in, it just understeers wide.
Druids is ALL about carying speed in + through the corner to then have great exit speed as this is where an overtake is then possible before lodge.
If you were to take stus line your braking too much + loosing too much entry speed...Trust me ive tried it many times....
Also you have somebody up your "inside" on the entry. In a race that is...!!!!!!
I have a vid somewhere [of my incar]of last years RS day, but it might take a while to find....[8|]
That line isnt too bad in the wet , but its still way too deep...
I know / knew Stu well + thats his little personal line. BUT he constantly tries to tell everybody he takes round that, that is how druids is taken.
We have had many , sometimes heated disscusions about it, but he,s insistant he is correct....[8|][8|][8|]
I suppose "we" both ,,,, "think" we know how to do it....[][][][][][]
Im not saying that i "know it all", That would be foolish, Its just "that" line is in my eyes is wrong.

 

[edh]

It wouldn't be my choice either Dave - and I've never seen anyone else propose this line. I just happened to have discovered it myself by mistake last week
If we were having a discussion about race techniques, and I claim no expertise here, then the issues are quite different from trackdays.

For trackday drivers I think that the main problem with Druids is going in too fast - you can lose a lot of time trying to sort out the resulting mess, and if you're running too wide as you exit you have to back off or risk dropping a wheel onto the grass on the outside. Far safer on a trackday to go in a little slower & get on the power nice & early (and have the car stable as you go over the hump / tarmac change on exit).

I bet more cars come off here on trackdays than on all the other corners combined....

Interesting website Neil - I can add that to my list of excuses []