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21 Turbo Quadra 4wd system
- Thread starter DaveL485
- Start date
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Deleted member 486
@la21t I'm not quite sure how a Swedish style plenum will help response? Everything I have seen suggests that it would be worse because of the larger volume of air inside them compared to a normal inlet manifold...
My biggest worry with a Swedish plenum is that, unless it's been properly designed and tuned on an accurate flow rig, there can be quite a large difference in the volume of air going in to the different cylinders, therefore giving the potential for cylinders to be rich or lean depending upon how the car is set up. Even if it is properly designed I would only want to be putting this on if the ECU can fuel trim each cylinder individually. Unless you're going for crazy power (@DaveL485 levels) then a "normal" is probably a better bet. Not saying it won't work just now sure how it would work!
I agree with the exhaust side of things though! Certainly worth getting an exhaust that can flow the extra gasses!
My biggest worry with a Swedish plenum is that, unless it's been properly designed and tuned on an accurate flow rig, there can be quite a large difference in the volume of air going in to the different cylinders, therefore giving the potential for cylinders to be rich or lean depending upon how the car is set up. Even if it is properly designed I would only want to be putting this on if the ECU can fuel trim each cylinder individually. Unless you're going for crazy power (@DaveL485 levels) then a "normal" is probably a better bet. Not saying it won't work just now sure how it would work!
I agree with the exhaust side of things though! Certainly worth getting an exhaust that can flow the extra gasses!
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Deleted member 486
The way the curve climbs reminds me of the V16 BRM engine. Due to the way the supercharger was geared, at one point in the power curve a 1000rpm increase resulted in a jump of over 300bhp!! That must have been an interesting beast to drive...
la21t
Well-Known Member
Thank you @stavers given your job I'd sooner listen to you than 'forum chat' - I was and still am in a dilemma over this until reading that.
Given the cost involved to do it, I think I'd be better off going bigger valves eh?
As for the way it drove, it is very urgent and took @am21t in his RS6 completely by surprise. I have a mate with a 2008 c63 AMG and rolling side by side at 50/60 with me in 3rd, I'll easily pull 2-3 car lengths on him while he waits for kick down etc and then naturally I'm blown out the water but he said 'he expected a much easier time of it'.
Trouble is, it runs out of breath as quickly as it gains it.
Given the cost involved to do it, I think I'd be better off going bigger valves eh?
As for the way it drove, it is very urgent and took @am21t in his RS6 completely by surprise. I have a mate with a 2008 c63 AMG and rolling side by side at 50/60 with me in 3rd, I'll easily pull 2-3 car lengths on him while he waits for kick down etc and then naturally I'm blown out the water but he said 'he expected a much easier time of it'.
Trouble is, it runs out of breath as quickly as it gains it.
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Deleted member 486
I would certainly be looking at the best ways of making the engine breath as best you can. Getting that air path in to the turbo as short & smooth as possible will help with compressor efficiency (thus meaning that cooler air comes out of the compressor so you get a better charge). Getting it as short and smooth after that will help a lot with the lag. I do think that the 90° bend from the throttle body in to the plenum is a weak point on the 21, not helped with another sharp bend at the bottom of the plenum in to the main part of the runners in terms of smooth airflow.
For me, lag is mainly down to two things: getting the turbo spooled up with the exhaust gasses & getting the compressed air in to the cylinders. Having the shortest run with the smallest volume of air after the compressor outlet will help quite a bit - & a Swedish plenum is the opposite of that (but probably better for a large amount of power but you will get that trade off).
To bring that knee point forward I thing a turbo re-trim (which it sounds like you're doing) will help quite a bit. It really looks to me as if the turbo is too big as there is a very small area of peak torque.
Bigger valves and polished ports could well help - but generally speaking on a turbo engine the most important thing is to get the combusted gasses out of the engine. If I were doing a T/C engine from scratch I would make the exhaust valves bigger than the intake - you have the turbo to help overcome any small loss in efficiency from having smaller intake valves which is more than made up for by the better exhaust breathing. N/A engines is completely the other way round - you need the inlet valves big as you haven't got anything helping the air in!
Anyway - I digress...
Craig Righton
Member
Interesting.
I was thinking about inter-coolers lately. The one off Trev's old quadra was one off a Master van.
Apart from having plastic end caps I think it will make a good cooler. The core is thin but its surface area is large (fill the cut out in an evo bumper).
Link to size here..... eBay item [HASHTAG]#141527792888[/HASHTAG]
Discuss...... Lol
I was thinking about inter-coolers lately. The one off Trev's old quadra was one off a Master van.
Apart from having plastic end caps I think it will make a good cooler. The core is thin but its surface area is large (fill the cut out in an evo bumper).
Link to size here..... eBay item [HASHTAG]#141527792888[/HASHTAG]
Discuss...... Lol
Last edited by a moderator:
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Deleted member 486
Hmm - interesting.
Of course it's always a trade off between surface area & pressure drop. In an ideal world it would have a large surface area and a very low pressure drop but that hardly ever happens!
Without getting something flow tested and then run with temperature and pressure measurements at each end of the 'cooler it's pretty much pot luck as to whether it'll do the job well enough or throttle the air flow too much! & then you want it as small as possible to reduce the air volume and thus the lag...
Of course it's always a trade off between surface area & pressure drop. In an ideal world it would have a large surface area and a very low pressure drop but that hardly ever happens!
Without getting something flow tested and then run with temperature and pressure measurements at each end of the 'cooler it's pretty much pot luck as to whether it'll do the job well enough or throttle the air flow too much! & then you want it as small as possible to reduce the air volume and thus the lag...
DaveL485
Staff member
If you look in the upper right you'll see the 'loading' icon flashing as the picture uploads. If you wait a few seconds while it does so the 'Choose file' box vanishes and then you'll see the image as-per desktop when you choose to insert as full or thumbnail.
You impatient cock.
DaveL485
Staff member
I disagree with that...i'd only put the onus on exhaust valves if I were running a large hit of Nitrous Oxide as well. If we took a round straight tube with matching diameter to the valve head as 100% flow efficiency then the normal inlet port flows at about 50%. The exhaust port doesnt have this issue, as the air already uses the full circumference of the valve seat due to the fact it's going into the seat from all around the chamber. As long as the port is big enough then it should hit >65% efficiency or more because the valve seat is being used more effectively. Even the shape of the short side bend is not that critical because it's not having to guide the air into a seat like the inlet, where the inlet charge can skip across the short side of the valve for example.
Edit to add: OE 21 Turbo Inlet valve diameter 43.9mm, Exhaust valves 37mm
Craig, that Master cooler isn't too bad but size wise of endcaps, flow, and the sharp bends will limit you if you're seeking big power....however anything below a standalone ECU effort though it should be fine.
Craig Righton
Member
Dave,
Not going for massive power. Been there/done that.
Going to run 17-18psi, with head work,matching the manifolds, t34 with .48 cossie housing, front mount, got the nice downpipe and side exit exhaust already as you know, cossie fuel reg, would love another Nick Hill chip and a front mount.
Ideal would be 235-240 bhp and get a standing quarter of low 13s,
Not going for massive power. Been there/done that.
Going to run 17-18psi, with head work,matching the manifolds, t34 with .48 cossie housing, front mount, got the nice downpipe and side exit exhaust already as you know, cossie fuel reg, would love another Nick Hill chip and a front mount.
Ideal would be 235-240 bhp and get a standing quarter of low 13s,
Turbjj
Well-Known Member
DaveL485
Staff member
You still having the manifold? Still at Lee's I think.
Craig Righton
Member
DaveL485
Staff member
Yeah no probs buddy, i was just making sure...I dont mind holding it for you but if you didnt want it i'd stick it up for grabs.
la21t
Well-Known Member
Whoa were you visited by the 3 ghosts last night?
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Deleted member 486
For an N/A engine this is the really important part as you have no additional pressure to get the air past the inlet valves but you do have the piston to help push the exhaust gasses out. With a boosted engine you do have something helping you on the intake side. If the exhaust ports are too small then the flow ends up going supersonic which massively reduces the efficiency of the exhaust port thus strangling the engine.
I know that a lot of boosted engines have an inlet port larger than the exhaust port but this is because they are based upon an N/A engine and the cost involved in re-tooling the head to swap the large port over would be too high to be feasible (speaking from experience on JLR 5.0 V8 - but the theory is the same). When the guys were running CAE on the boosted engine it was always the small exhaust port that was causing the issues - swapping to small intake port and large exhaust port would have gotten round this problem but it was too expensive - but the basic size of the ports was set by the N/A.
