///// how much gain is there in reducing intake temps ? ////

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
Hi all,

I've been running my grill blocks year round with seemingly no I'll effects ( I blocked off the top where the vw logo is , the large lower opening and the driver side grill ... of course the passenger side lower grill for the intercooler was left open tho I block off 1/2 of that in the winter ).

Anyways , per the scan gauge my water temp is 195 and intake temps tend to be +20 or more over ambient (sometimes a little lower but not real often).

Anyways, the other day I decided to make another custom upper block with the upper right of the block cut out to allow cool outside air into air intake a little easier (a more direct path instead of sucking air from under the car indirectly).

With that I had to take off the old block to use as a basic template to make the new one ....

I got everything cut out on the new grill block but called out to do a 2 hour run (I do expedited / time critical deliveries so I didnt have time to mount the new modified grill block.

Anyways, in driving without the block I noticed on the average about a 4 degree drop in water temp and about a 7 degree drop in intake temps per the scangage ...

I originally left the blocks on because it helps in the winter for warm up , possibly better aerodynamics, prevent bugs from getting into the ac condenser .

But now that the grill block is off ....What potential gains power / economy wise are there in dropping intake temps about 7 degrees?

I may run the rest of the tank without the block to see what happens also but thought people who dyno and hypermile may know the answers already

Thanks in advance for any and all help.

Andrew
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
cooler the air is, the more O2 molecule there are per volume of air, equals more power but only at full power demands. realistically no power is gained at all becuase your ECU is measuring the temp and amount of air coming in and adjusting the fuel accordingly.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
Your existing air intake is already doing the cooling as well as supplying more than the required amount of air for the engine. No gains here either. If you modify you're just going to make things worse.
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
Driving on the track I could feel the ECU pull timing and the loss in power if AITs got above 130F. Doubt you'll reach that on the road, except maybe sitting in traffic on a very hot day. So as posted above, you're not going to see any change, positive or negative, to higher temps that you'll reach in street driving.
 

meerschm

Top Post Dawg
Joined
Apr 18, 2009
Location
Fairfax county VA
TDI
2009 Jetta wagon DSG 08/08 205k buyback 1/8/18; replaced with 2017 Golf Wagon 4mo 1.8l CXBB
Hotter air-less fuel- better mpg
No, Hotter air, higher temperature; mass flow sensor readings combined with temperature value as input to the computer (I assume your tune includes these parameters as the oem program did)

Then the fuel injection duration values and request for turbocharging is adjusted in response to the driver desires, considering these values.

Remember that this is a diesel, not a gas engine that is programmed to run near the stoichiometric fuel/air value to protect the emissions equipment from fuel poisoning. It runs on the lean side, so that there is always more air than needed to burn the fuel injected.

When the air is hotter, the turbo will still compress the air to make sure there is enough to burn the fuel injected.
 

turbobrick240

Top Post Dawg
Joined
Nov 18, 2014
Location
maine
TDI
2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
I wouldn't run the grill blocks in the summer. The engineers at VW knew what they were doing when they designed the grille and cooling system. Saving a penny or two in fuel isn't worth overheating the engine.
 

Powder Hound

Top Post Dawg
Joined
Oct 25, 1999
Location
Under a Bridge, Crestview, FL, USA
TDI
'00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
Tests generally show, particularly for diesels, that the cooling action from the intercooler is nearly identical to the temperature reduction in the exhaust gasses. Ergo, you lose nothing in efficiency and will gain something there in terms of intake charge density. In my mind, the biggest gains are in the reduction of stress on the engine during all phases of the combustion cycle due to the reduced temperatures.

Cheers,

PH
 

Curious Chris

Top Post Dawg
Joined
Jun 11, 2001
Location
Pineview GA
TDI
Jetta Wagon 2003 RIP Rockford IL
if you are tuned and hold it to the floor the stock intercooler heat soaks after 10 seconds on a hot day and the fueling drops accordingly. So power goes down. I did a test on my dearly departed 2002 Gold running RC2, Jeff asked for fueling results after 15 seconds at full throttle, so I logged it and yup it dropped, put a big FMIC in my car and problem was solved.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
My 764s and gt2052 and stage 6 tune build had a 3"x27"x7" FMIC. Still not enough to stop heat soak. Ended up doing a dual fog shot pre and post turbo of just water. World like a charm. Until I ran out of water. But I just ended up using the tears of Prius owners. Works out fine!
 
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