View Full Version : Rolling road result
I just got back from an IMOC organised rolling road day at Millway Motorsport in Andover.
First run 216BHP at flywheel (just after a 2 hour journey)
Second run 225 BHP at flywheel (car cooled down slightly, but still red hot!)
It was a hot day today.. not the best day for a rolling road session and my interwarmer is losing me a lot of power. I'm still a bit disapointed with the results considering its running 13psi on a hybrid CT26...
Bring on the boot mount intercooler!!
Jiff Lemon
04-08-2007, 16:44
Ah, you['ve got the interwarmer postion haven't you?
Charge cooler for the win i say! (but then again, I don't do turbos!)
Did they get any inlet temps at all or was it just power runs?
can we see the map ollie, where is the intercooler?.. 225 at the fly sounds a tad low.. what have you got on the engine i.e; exhuast system, intake.. cooler.. turbo type?..
Marksman
05-08-2007, 22:32
[armchair / keyboard mechanic mode on] I wonder if you might get more power by turning the boost down? With the interwarmer getting swamped and things getting hotter and hotter maybe a "comfy" 8-9 PSI might yield more power than a heatsoaked 16 PSI? [mode off]
Just an idle thought.
Owen.
Marksman
05-08-2007, 22:47
[fallsoffchairsmiley]
Owen.
Owen is actually spot on the money with this one.
More boost =more heat =less power.
A similar thing happened with the four while attepting to get more out of it, i found that by reducing the boost from a previously higher level, the car ran stronger for longer before heat became a problem. :) :thumbsup:
That's very typical of a CT26 really. Hairdryer mode over 15psi. unless you've got a shit hot intercooler or chargecooler, then you're pretty much goosed. 12psi will net you the same as 15 in run after run and the heat output is a lot lower and therefore more reliable
cartledge_uk
06-08-2007, 07:15
The problem with the day was their printer and computer link up was down so no printouts. But it was only £20!
All the tubbys were down on the day, and the N/a's were spot on it seamed
Interesting theory about turning the boost down...
My 1.5 has an unknown hybrid CT26, it was running at 13psi. My exhaust is restrictive (only 2.5inch) and my interwarmer sits in the Mk1 SC location. The engine is red hot after a 5 minute run and takes an age to cool down.
I've picked up a large boot mount intercooler which I'm hoping will do the job.
As Tim mentions, there was no print out for the day... not that I'm bothered with only 225bhp!
a swift move to the boot will net some helpful results by the sounds of it ollie, a decat doonpipe may also help free up some of them horses.. aside overboosting in 1st gear lol.
Owen is actually spot on the money with this one.
More boost =more heat =less power.
not entirely true. heat is energy, energy is power, the more heat youve got, the more power youre producing
the issue is that you arent harnessing the extra heat. the engine cant safely run as hot as it is being asked to, so it compensates by running at less-than-optimum settings thus losing the power (assuming the engine has a knock sensor that is, otherwise it will just detonate until you stop it!)
having the heat isnt the issue at all, its managing the heat. and every engine has its limit, so you usually end up trying to lose the heat pre-engine (wasted energy really) with intercoolers, etc. in this scenario you are obviously overloading the charge cooling systems beyond the capacity they can cope with, getting heatsoak, and thus the engine is losing power. as said, backing the boost off a bit would probably yield higher power output overall. the extra heat was obviously just present due to the higher than normal ambient temperature, but if you get heat issues at more normal temps then you need to look at the setup more carefully, since it probably means the turbo is way too big for the current engine setup
i knew what you meant though by saying that extra heat results in less power, just thought id clarify it.
if the engine could cope with the heat internally though then youd want the charge hot. the charge gets hot through compression (as well as the unavoidable heat transfer from the turbine housing through to the compressor housing), hotter gases are at higher pressures. cool the charge and you reduce the pressure (the reverse of what the turbo just did). reduce the pressure and you lose energy. on the other hand, too much heat into the engine results in it running too hot and having to back itself off to compensate, and then you lose power that way instead.
its a conundrum. in the real world you simply settle for the inefficiency of the setup because it still makes loads more power than running normally aspirated, and thus run a charge/intercooler(s) to lose the heat pre-engine and then gain it back through running the engine at the edge of its heat handling capacity.
im being a bit pedantic here mind, but its a saturday and im bored lol
cooling the air increases its density, thus more matter can be compressed into the same space, the principle of turbocharging, made (not as bad) / efficient with cooling. its right about the heat energy loss, if it wasnt controlled we'd be all oversized / expanded and seized up lol:thumbsup:
not entirely true. heat is energy, energy is power, the more h
Not strictly true in itself for the intake side of an engine. It's more a case of the greater the change of heat in the cylinder the greater the power developed.
Firstly, say for example your cylinder temps hit around 900c peak, air entering the cylinder at 25c would increase in pressure relatively more than air that entered at 100c (greater change in temperature in the same volume therefore a greater pressure change), producing more power from the cylinder.
Also at 100c (fairly realistic turbo output temperature) air is some 30% less dense than air at 25c (therefore holding 30% less oxygen by volume and thus able to fully combust 30% less fuel), a big power loss that can be regained through lowering the temperature of the air before it gets to the intake valves.
A well-tuned engine should never run to the limit of it's intercooling capacity, the air going into the engine intake should always be as cool as possible allowing the engine to injest a maximum of oxygen.
Heat = energy = power is valid for the exhaust side of the system though, where a given mass of exhaust gas will have a greater kinetic energy at a high temperature than would an equal mass of colder gas.
Not strictly true in itself for the intake side of an engine. It's more a case of the greater the change of heat in the cylinder the greater the power developed.
Firstly, say for example your cylinder temps hit around 900c peak, air entering the cylinder at 25c would increase in pressure relatively more than air that entered at 100c (greater change in temperature in the same volume therefore a greater pressure change), producing more power from the cylinder.
Also at 100c (fairly realistic turbo output temperature) air is some 30% less dense than air at 25c (therefore holding 30% less oxygen by volume and thus able to fully combust 30% less fuel), a big power loss that can be regained through lowering the temperature of the air before it gets to the intake valves.
A well-tuned engine should never run to the limit of it's intercooling capacity, the air going into the engine intake should always be as cool as possible allowing the engine to injest a maximum of oxygen.
Heat = energy = power is valid for the exhaust side of the system though, where a given mass of exhaust gas will have a greater kinetic energy at a high temperature than would an equal mass of colder gas.
made myself look a bit silly there! youre all quite right, il sit in the corner and be quiet, or maybe sign myself back up for primary school so i can go and re-learn the fundamentals of science lol im really not as retarded as i just made myself look there, i promise!!
No worries mate ;) I spent a day reading plug wiring diagrams upside down the other day, then sh*t myself when I ran out of connectors at 11 at night 15 miles from home...... lol
too much information in the hard drive jim :mrgreen:
too much information in the hard drive jim :mrgreen:
something like that!
you learn something new every day....and forget something old
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