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

    • Yes. Probably, given that there is only access from the bottom end of it, go with a drill bit. Don't start too small. 7 or 8mm is probably the right size. You want something that can make a big enough hole to do some damage, but not so bit that it clashes with the steel or binds up and breaks your wrist. A slow speed is probably a good idea too. Once the rubber is destroyed, you then have to get the crush tube off the stud, which will be the whole heat/oil/cutting exercise all over again, but this time with the need to strictly avoid damaging the stud (any further than the corrosion might already have done.
    • We replaced the connector just because we could and it was still there, once we swapped the injectors around it stopped. The injectors were something I had thoughts of replacing even before I first started the engine and in hindsight I should have 
    • Not too sure just yet, want to have a go at doing what I can myself, but to start with want someone to cast their eye over it tell me what needs doing to get it running and back on the road, so anyone with great overall knowledge would be ideal.
    • I personally would go with cutting out the rubber. Then deal with getting sleeve off separately. Rubber can be painful to cut, it loves to jam up cutting tools. I normally have success with drill bits, deburr bits, angle grinders, jigsaw, reciprocating saw, and never forget... fire. Obviously different tools won't work in all locations you're trying to work with, and you need to be comfortable with each. You personally may be happy slowly slicing it out with a razor blade, if you are, go for it with one too! Feel free to wait for others to weigh in also on their thoughts.
    • So ... I got everything disconnected and started dropping the frame. Three of the four mounts started to come down but the fourth one (the one with the nut that gave me all the trouble) won't budge. The inner metal sleeve stays up tight against the chassis rail although the outer part of the mount drops a bit (and can be levered quite a lot more) but it's just stretching the rubber bushing. So I reckon there's some serious corrosion inside the inner sleeve and holding it tight to the lug at the top of the bolt. Tried everything I can think of so far: penetrating oil, whacking the top of the sleeve to vibrate it and wedge a screwdriver blade in there. I also tried to turn the inner sleeve a bit by hitting it with a chisel at the bottom. It's stuck solid. What do you think about cutting the rubber with a blade so I can drop the subframe around it anyway. Then worry about getting the inner sleeve off after? Will that work? Is it gonna give me even more problems?
×
×
  • Create New...