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The Q4 has an exhaust gas temperature probe in the front pipe and a gauge in the car
Does anybody here know what the temperature should roughly run at ???
hi
front pipe?
when the sensor on exthaust manifold (before turbo)
you can see ~920C when full throttle with std ecu eprom.
our std ignition map highly retarded and very rich fuel when full throttle
more retard + more fuel = high egt
hi
front pipe?
when the sensor on exthaust manifold (before turbo)
you can see ~920C when full throttle with std ecu eprom.
our std ignition map highly retarded and very rich fuel when full throttle
more retard + more fuel = high egt
Its in the front pipe after the turbo .................. at the moment its reaching around 600 but thats just on short journeys
More fuel in the F/A ratio cool the combustion temperature down. Lean mixtures give more power but run hotter. Problem is your aluminium pistons melt at 1200C
If the timing is retarded to much the Fuel mixture do not burn completely in the combustion chamber and some fuel will still burn in the exhaust manifold. Some racers used this to spin the turbo on the starting line but is very dangerous.
If you run high boost you can see 970 c too. Just try to take off your foot from the throttle pedal if you see more than 1000 c. If you have the sensor after the turbo you will see about 150c less so if you see 700c the true temperature is about 850c. This temperature is completelly normal but have in your mind that the best temperature in full throttle is about 900c this means the engine is giving the max
More fuel in the F/A ratio cool the combustion temperature down. Lean mixtures give more power but run hotter. Problem is your aluminium pistons melt at 1200C
If the timing is retarded to much the Fuel mixture do not burn completely in the combustion chamber and some fuel will still burn in the exhaust manifold. Some racers used this to spin the turbo on the starting line but is very dangerous.
I want to explain some my experience
more fuel cool down in cylinder temp its true
when knock occure, ecu send more fuel and make ignition retard and boost down.
But
when I measure our std Q4 chip I see ~930C full throttle and near ~10 afr !
then, I reprogram eprom, also I make it 6-7 Q4 in turkey
at full throttle afr ~11.5
and some rise up ignition timing (listen knock with headphone ofcourse)
egt down to ~850C
is it dilemma ?
I want to explain some my experience
more fuel cool down in cylinder temp its true
when knock occure, ecu send more fuel and make ignition retard and boost down.
But
when I measure our std Q4 chip I see ~930C full throttle and near ~10 afr !
then, I reprogram eprom, also I make it 6-7 Q4 in turkey
at full throttle afr ~11.5
and some rise up ignition timing (listen knock with headphone ofcourse)
egt down to ~850C
is it dilemma ?
If We are in this topic i have question too :)
had some problems with EGT, especially in very cold days, so made some improvements by setting proper AFR and watching EGT, now afr around 11-12 in all rev and boost range, but EGT is still a little bit too high (more than 900c on WOT in high rpm's)
and it's little confusing but to gain this afr i almost maxed 630cc deka injectors on high bost and rpm's
any advices ?:) (no knocking at all when reading knock signal from sensor).
regards
W
High EGT is also because of backpressure too! What is your turbo?
I agree with Mpampis, when running high power, the hot gas need to get out of the engine as well. With a small turbo meaning turbo with small turbine wheel or too small exhaust, some gas can be trapped in the combustion chamber. This can cause detonation. And it will show in the EGT.
And now I have to be careful as this was the most successful turbo car up to the VW GTI. I have not tried to push the max on my Q4 yet, so I don't have an opinion about the engine's reaction. On the turbo TS 262/7 whp came at 0.75/0.8 bar boost and with 800C EGT. This was with standard NA cams Intake locked.
In this regard I question the "small" exhaust cam in the Q4s. It should be fine for the "normal" power up to 250hp. But even then I am for Steve Webb's suggestion to use the intake cam on the exhaust side and a NA Lancia cam on the intake. This will make the same power at lower boost and improve the gasflow out of the engine, be more safe with an good exhaust.
I have seen pistons from a turbo car with a few spots that show melting on top of the piston. The rest of the piston looked fine, but the shape of the piston changed and it was loose in the sleeve. Unfortunately the car did not have a EGT gauge on.
I am waiting for Guy Croft's book as he has a defnite oppinion about the ratio between intake and exhaust cams on turbo cars. Until then I stand by my opinion.
I had a conversation with Enrico from Scara73 about camshafts. The point was the exhaust camshaft that there is no need very high lift because the turbo will spool up at very high revs. 9.6 lift for exhaust is the best. In my opinion if you want for more, a nice ported head or bigger exhaust valves are nice idea instead of higher lift than 9.4 exhaust camshaft.
I agree with your last post Mpampis. The standard Q4 exhaust cam has a 7.2mm lift and 210 deg duration, very small.
Standard NA TS engine has 9.5mm lift and 236deg duration on both cams and it worked well with a turbo.
The down pipe after the turbo is very important and little back pressure in the exhaust. Gas flow from a high pressure to a low pressure. You have the high pressure in the exhaust manifold and now you need the low pressure in the exhaust while the gas is flowing. A exhaust with long straight pipes are better, preferably with one large non baffle silencer. If this is good, the turbo will be more effective and the hot gas will flow better from the engine as well.
See downpipe with smooth exit from turbo with no turbulence.
http://s1224.photobucket.com/user/corriedewilde/library/Down%20pipe%20and%20Aircleaner
I had a conversation with Enrico from Scara73 about camshafts. The point was the exhaust camshaft that there is no need very high lift because the turbo will spool up at very high revs. 9.6 lift for exhaust is the best. In my opinion if you want for more, a nice ported head or bigger exhaust valves are nice idea instead of higher lift than 9.4 exhaust camshaft.
Mpampis you obviously researched this. So for interest sake, what cams are you using in your Q4?
I still have the stock cams but i have ported and polished head. I will replace the cams with 11.2 in and 9.6 ex. It is enough specially with gt3582r turbo i will have enough power without crazy and high boost
If you do a dyno run with the standard cams, please share the results with us. I would prefer to not use high lift cams, so this result is of interest.
With previous turbo i had 380hp at 1.5 bar.
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