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No you don't get a pressure drop with a large IC. A too small one would get you a pressure drop.
A large one will give you a bit more lag (because there are a little bit more volume to fill), but no drop in pressure
These are indeed correct m=53 lb/min, Cp=0.25, U*A=20.1
lets start by assuming that the intercooler outlet temp = 140
Q = m * Cp * DT
Then DT = (350 - 140 ) = 210 and Q = 2782.5 BTU/min
Cooling air flow = 85.33 lb/min
DT for the cooling air = Q/(m*Cp)
DT = 2782.5 BTU/min / (85.33 lb/min * 0.25 BTU/lb-f) = 130.4 F
since DT = T out - T in, then 130.4 = T out - 85 and T out = 215.4 F
So the cooling air inlet is 85 F and the outlet is 215.4 F, and the turbo air inlet is 350 F and the outlet is assumed to be 140 F. Now calculate DTlm:
P=0.792, R=0.62, and F=0.75
DT1=134.6, DT2=55
DTlm=(134.6-55)/ln(134.6/55) * 0.75 = 66.7
Now calculate a new Q, Q= UA * DTlm
Q=20.1*66.7=1340.7
Since this isn't the same Q we got when we assumed an outlet temp of 140 deg, we have to get a new outlet temp and run through all this again.
I'll assume a new intercooler outlet temp of 170.
Q=(m*Cp*DT)=2385
cooling air DT = 2385/(85.33*0.25) = 111.8
Cooling air outlet = 85 + 111.8 = 196.8
P=0.68, R=0.62, F=0.84
DTlm=97.3
Q=1954.7 still not close enough
Last try!
T IC out = 182
Q=(m*Cp*DT)=2226
cooling air DT = 2226/(85.33*0.25) = 104.4
Cooling air outlet = 85 + 104.4 = 189.4
P=0.63, R=0.62, F=0.88
DTlm=111.0
Q=2232 close enough SPOT ON
To add my experiences, Ive recently purchased a WaterInjection kit to bring temps down and for some methanol aid.
I purchased a Nordskog air Temp aswell and tapped a sensor into my intake manifold.
To my utter amazement my car produced a max of 36deg Celsius whilst boosting hard in simulated drag mode !!
I am still using standard S2 inter cooler and test was done with water injection switched off. The ambient temp on the day was 24 deg Cel.
I did not believe the sensor and logged intake temp with vag com ... result similar temps.
So my conclusion .. a big effiecient turbo does not make lotsa heat to require a monster intercooler.
I will be changing mine , but mainly to help with the airflow...
BTW: water injection brought the temp down by 5-7 deg cel.
on another note: a friend of mine has a POLO GTi standard except for a chip modification. The intake temp on the car goes upto 90 deg Celsius...
Another Golf GTi I've measured was @ high 60's standard !!
Turbo very inefficient when boosting them high...
S2 Coupe fully built.
10.9 1/4mile 0-100 in 3.5secs
Precision 6262 turbo
The stainless pipe is 3mm thick? Thats pretty heavy. Can you get thinner stuff? 1.5 or 2mm should be plenty thick enough, I would think.
I'd like to order a crossmember if you're thinking of having some made
Yeah that's true John, The 3mm Stuff is quite weighty. - Like you said im sure 1.5mm would do but its a bit late now
Reg, the crossmember. Im just trying to source some more of that 40x40mm box section. Then ill get the welders to make a couple more. - Another member wants one too.
--
On a different note, I have a question about the Snub Mount. In order to get the Corssmember to fit i had to take the Rubber stopper off. Now leaving the Snub mount exposed. I presume this is ok. Please let me know if its not. Im not really sure what that thing is for anyway apart from holding the crank look tool..
well done s2 bo, my hat goes of to you. its reasuring to know that us boys with the oe front bumper can get soemthing that big behind it and still keep the aux rad.
good write up aswell!
1995 B4 Audi 80 S2 avant 267bhp and 326lbft *sold*
The snub mount is to hold the engine down so it doesn't come up out of the bonnet when you drop the clutch, or go out through the IC when you hit the brakes I think I'd rather go for a CM that allows me to keep it.. Should be possible as others have done it. IIRC there are 2 different rubber bungs, a big one for cars with AC and a smaller one for cars without.
The snub mount is to hold the engine down so it doesn't come up out of the bonnet when you drop the clutch, or go out through the IC when you hit the brakes I think I'd rather go for a CM that allows me to keep it.. Should be possible as others have done it. IIRC there are 2 different rubber bungs, a big one for cars with AC and a smaller one for cars without.
Thanks John,
Thats ok though, I haven't modified the Mount at all. At the moment it sits very tightly right under the crossmember so theres no chance of it lifting up. Theirs nothing stoping it puncture the IC though. Ill have to get a stopper bracket welded on to the front of the Crossmember to stop the snub busting in to the IC.
The snub mount is to hold the engine down so it doesn't come up out of the bonnet when you drop the clutch, or go out through the IC when you hit the brakes
That little thing stops that from happening!
Better make sure I restrain the lil' ******!
I have come up with a solution for the snub mount, leaving it at it original state. I will be attaching a bracket to the crossmember so that the mount is cupped Very similar to the bracket on the stock corssmember.
I am having 3 more crossmember made up for forum people and just want to make sure that the 3B sump mount is in the same place as the ABY one. Is this the case?
If not it will make things a bit more complicated.
How much did a cross member cost to make up Bo? and how have you attached the Aux rad?
AFAIK Snub mount is in the same place as the cross members are interchangable on the ADU, ABY and 3B when members previous upgraded intercoolers to OEM ABY or ADU ones.
I have a V6 crossmember and the mount is in the correct place but probably best to get a confirmation from Doug / Martin
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m=53 lb/min, Cp=0.25, U*A=20.1
That little thing stops that from happening!
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