Jump to content
SAU Community

Recommended Posts

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

Link to comment
https://www.sau.com.au/forums/topic/193965-power-lost-on-hot-days/
Share on other sites

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:

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)

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.

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."

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:

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.

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 :-)

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

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
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:

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • It is a kunfine Android screen . Does anyone know the wirering diagram of the fuga ??
    • just an update to this, poor man pays twice  Tried sanding down the pulleys but it didnt do the trick. Chucked another second hand alternator in the na car which I got for free off my mate and its fixed the squelling. Must have been unlucky with the bearings.    As for my turbo car, I managed to pick up a cwc rb alternator conversion bracket + LS alternator for 250 off marketplace, looked to be in really good nick. Installed it , started the car and its not charging the battery.... ( Im not good with auto elec stuff so im not sure if this was all I needed to do but I verified such by using a multimeter on the battery when the engine was running and I was only getting 12.2v )   I had to modify the earth strap for the new LS alternator , factory earth strap was a 10mm bolt which did not fit the bolt on the LS alternator which was double the size so I cut it off , went to repco bought some ring terminals that fit, crimped it onto the old earth strap and bolted it up to the alternator , started the car and same issue. Ran like shit and was reading 12.2 at the battery.  For a "plug and play" advertised kit thats not very plug and play but alas.  My question is , am I missing something ? Ive been reading that some people recommend upgrading the stock 80 amp alternator fuse to a 140 amp but I dont see how that would stop the alternator charging especially at idle not under load.  Regardless ive pulled it out and am going to get it bench tested by an auto elec tomorrow but it would be handy to know if ive missed something silly or have done something wrong.   
    • My wild guess is that you have popped off an intake pipe....check all of the hoses between the turbo and the throttle for splits or loose clamps.
    • Awesome, thanks for sharing!
    • To provide more specific help, more information is needed. What Android screen? What is its wiring diagram? Does the car's wiring have power at any required BAT and ACC wires, and is the loom's earth good?
×
×
  • Create New...