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Power Lost On Hot Days!

ashley12345

By ashley12345,
in Engines & Forced Induction

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ashley12345 Apprentice

ashley12345

Posted
Posted

Hi....

Ive recently got an R32 GTR and was wondering if you guys notice a dramatic different in the power on say a 30 degree day vs a really cold night...

On a hot day it seems very sluggish in comparison....

How much power would you estimate is lost on a very hot day vs a cold night...

Thanks

Ashley

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DRD-00F Grand Master

DRD-00F

Posted
Posted

HEAT SOAK!

Yeah it makes quite a bit of difference for me, I can normally bang in just under a bar of pressure on a cold night, but I won't see past ten PSI on a hot day...

Get some Cold Air Induction and it should do better :rofl:

sh@un Grand Master

sh@un

Posted
Posted

i think it was a reduction in power of around 1-2% for every 5 degrees the inlet temp goes up. but don't quote me

the main thing you'll notice in super cold weather is sharper throttle response and more low to midrange torque. in fact, the engine is more likely to suffer pre-ignition in really really cold conditions as the charge density at the point of peak torque will be much higher than usual (MAF based ECUs account for this though, and trim the spark advance accordingly)

~R33AzzA~ Proficient

~R33AzzA~

Posted
Posted

My understanding is that air is more dense on a cold day there for a better quality of air so ur A/F ratio's are more stable resulting in more power, On a hot day the density reduces causing a loss of power. Don't quote me thogh i could be wrong.

MrStabby Grand Master

MrStabby

Posted
Posted

FWIW, here's a definition of heat soak from here. This is why you use a turbo timer, it has nothing to do with loosing power on a hot day.

"When the engine is switched OFF, the cooling system becomes inactive and the residual heat in the engine from the block, head and exhaust manifold are transferred to the coolant and other engine components. The engine temperature actually increases after a hot engine shutdown. This is called 'afterboil' or 'heat soak' and can be damaging to engine life."

DRD-00F Grand Master

DRD-00F

Posted
Posted

No, the heat soak I meant was not getting enough cool air flow to the air intake...

You're talking about something different...

In 32 GTRs the air intakes are tucked pretty high up without a snorkel, so they can heat soak pretty well... the hotter the air, the less dense it is, so the less air that can fit into the cylinders... And without proper cold air induction, it sucks in all the hot air from the engines radiant heat...

And i dunno about you, but I use a turbo timer for the TURBO to cool down, it's not called an engine timer now is it? :rofl:

MrStabby Grand Master

MrStabby

Posted
Posted
My understanding is that air is more dense on a cold day there for a better quality of air so ur A/F ratio's are more stable resulting in more power, On a hot day the density reduces causing a loss of power. Don't quote me thogh i could be wrong.

Very close, the air is more dense on a cold day, so the engine management adds more fuel to maintain the correct A/F ratio, and you make more power because you're burning more fuel. And vice verca so less power on a hot day.

MrStabby Grand Master

MrStabby

Posted
Posted
No, the heat soak I meant was not getting enough cool air flow to the air intake...

I've never heard that referred to as heat soak before, but maybe i need to get out more. Google for heat soak and you'll see what i mean.

In 32 GTRs the air intakes are tucked pretty high up without a snorkel, so they can heat soak pretty well... the hotter the air, the less dense it is, so the less air that can fit into the cylinders... And without proper cold air induction, it sucks in all the hot air from the engines radiant heat...

My stock 32 GTR has a factory snorkel....so it doesnt pull any air from the engine bay YMMV.

And i dunno about you, but I use a turbo timer for the TURBO to cool down, it's not called an engine timer now is it? :rofl:

You're being a bit to literal :-)

DECIM8 Grand Master

DECIM8

Posted
Posted (edited)

Heat soak refers to what happens to the intercooler, i.e when the intercooler cant cool the air enough any more because its aluminum fins are heat soaked with well heat.. typically happens at traffic lights where the car can take on a shitload of heat.

The CAI system can also take on this but typically refers to the SMIC.. thats why a FMIC is alot better as the air charge is cooled much more efficently. hence why I bought the screwball thing

Edited by DECIM8
RBwhatever Veteran

RBwhatever

Posted
Posted (edited)

Heat soak is this, heat soak is that, nooo heat soak is this.

My goodness. Heat soak can mean heat soak on anything. It is as it states, soaking up heat. It doesn't have to be the pod or the motor or the intercooler. Heat soak can occur on a glass bottle in the sun, heck sponges suffer heat soak in hot water.

The terms should of been mentioned "heat soak of the _____".

Edited by KeyMaker
stolen_s15 Mentor

stolen_s15

Posted
Posted
Very close, the air is more dense on a cold day, so the engine management adds more fuel to maintain the correct A/F ratio, and you make more power because you're burning more fuel. And vice verca so less power on a hot day.

BINGO!

The basic idea of an engine is to ignite an air/fuel mixture and produce power. The more air we can get into a motor, the more fuel we can add to it, the more air/fuel mixture the more power we make. When temperatures rise air becomes less dense (less air in any given space), obiviously when temp decreases air becomes more dense (more air in a given space). Thats why on cold nights (when the car effectivly get more air) we get more power, and on hot days (car effectivly gets less air) we lose power.

:ph34r:

GeeTR Grand Master

GeeTR

Posted
Posted (edited)
How much power would you estimate is lost on a very hot day vs a cold night...

Depends on setup. When my R was stock, it felt like 25% lol... serious

Yeah it makes quite a bit of difference for me, I can normally bang in just under a bar of pressure on a cold night, but I won't see past ten PSI on a hot day...

Hence, the usefulness of EBC's

i try to keep away from the whole 'boosting' thing on a hot day

I never like this idea. Performance is total. What if it was 390 on a well planed track day? Would you baby your car? Thats for aftermarket (or PFC) knock sensors are for (not to mention human ears) I reckon the idea's to tweak your inlet temp correction to counter hot days. End results are end results, anything you can make compared to the guy next to you, is a profit smile.gif

this is where high quality coolers etc come into their own and shitty ebay bar and plate coolers start to sap power.

Trent, wasn't there a time, when bar and plate coolers where deemed superior to tube and fin? AVO's 1000hp coolers are still bar and plate... as are upper echelon HKS IC's i believe.

FWIW, here's a definition of heat soak from here. This is why you use a turbo timer, it has nothing to do with loosing power on a hot day.

"When the engine..."

For the purposes of the performance arena, i think "heat soak" refers to when the devices that are meant to move heat from intake air -> IC -> ambient air work in the opposite. This is noticeable in stand still traffic, where a IC can introduce ambient temps BACK into the IC -> intake air. This applies of course to intake piping and plenum's etc. F_ck Google.

My stock 32 GTR has a factory snorkel....so it doesnt pull any air from the engine bay

Meh to stock, 400rwkw+ deems AM pods and a proper CAI necessary for street application (im sounding like a c_nt tonight, must the the multiple personalities) :(

: To answer your original question, i think R's suffer from heat soak more then others, due to the surface area of all the piping. Twin turbos, twin intakes, twin filers, twin manifolds etc. My R when stock felt like a dash mounted marshmallow after a stand still period. Proper CAI's, bonnet vents etc help, but even after you have tweaked all your inlet temp correction values, you have to accept more heat means less power. You can imagine then why 5mins cruising in 5th at 80km/h in 50 weather has such a profound effect on throttle response and mid range (due to the ignition advance the ECU winds into (or should) in those conditions)

read into it, what you will loler'NZ-bungie jump

Edited by GeeTR

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