Intake temp high = Poo performance

[MattWij]

So its been a while since I have changed anything on the D40 and just wanting to shake the bugs out before I go for a 6 week trip end of April.

I've noticed that once the air intake temps hit 50 or higher I start to get really laggy performance, as in put your foot down and count to 3 before you start moving type thing.

Its not the end of the world off road but its crappy on the road, especially when trying to catch gaps in traffic entering the highway.

Anyone know of what can be done to help reduce intake temps? Its particularly noticeable when the car sits for more than 30 seconds the temp starts climbing, I'm guessing this is because of heat coming off the turbo is pooling. when there is no air moving around the car.

Would a jacket on the turbo help? has anyone done this? Will I have to whack on a snorkel? Or is there another cheeky mod I can do to help the situation?

I was out playing in the sand on the weekend and the air intake temp got as high as 80*C Although it was a 40*C day and the sand was hot.

 

[Old.Tony]

Without a snorkel your air is coming from the engine bay and is heated significantly by the air coming through the radiator/intercooler. Below 80km/h even with a snorkel there's enough engine bay heat to affect the air in the airbox so a snorkel won't see the problem disappear - but it will reduce it.

Other things you can do: hard pipe (or silicone) between baffle and intercooler - actually it's not the intercooler, it's really just a metal pipe fixed to the framework at the front because the intercooler's inlet is plastic and connected by a short section of rubber hose. It's done like this so the movement (from engine wobbling) can't weaken the plastic of the intercooler.

Don't replace the rubber hoses connected to the intercooler itself (no need, they're short pieces anyway). If you replace the pipe between the intercooler mount and the turbocharger you might consider doing away with the baffle. Make sure you have a nice piece of flexible hose on each end of the hard pipe to accomodate that engine wobble or it'll just pop the hose off.

You might see reference to people wrapping the hoses to insulate them. In my mind that can't be of a huge benefit - because the turbocharger is raising the temps to over 200C, the ambient temp under the bonnet of (say) 100C is rather cool by comparison so LESS insulation would be more beneficial - but what you're looking at is a large pipe with a finite surface area that will only transfer a small amount of heat before the air has raced past anyway. The message: rely on the intercooler and don't over-engineer the piping.

EGR blocking can help. As you squeeze the throttle, the EGR valve opens allowing exhaust gas to flow from the exhaust (at the manifold BEFORE the turbocharger's turbine chamber). This means the amount of gas entering the turbine chamber is less - less gas = less drive on the turbine = less boost. It's not a lot, but some people have noticed it. Block it and your turbo will spool quicker.

My turbo spools quite quickly now and all the piping is stock, as is the intercooler. The turbocharger isn't though - I bought a Forefront Industries turbocharger and it has a noticeably faster spool. I also removed my intercooler and ran some unleaded petrol through it a few times.

 

[MattWij]

Cheers Old.Tony. I have already done Hard Pipe upgrade and removed the baffle as part of that, EGR block was the first thing I did to the car and I have also upgraded the intercooler.

Hmm, it looks like the intake is just gonna get hot... Is a turbo jacket a good idea or not really of benefit? Would it help under bonnet temps?

The forefront industries turbo is tempting! Especially after I got a $700 quote for a snorkel installed. Did you have to get a remap for the new turbo or do you get benefit without doing one? I have already had mine remapped so don't really want to pay to have it done a second time... But I really don't need to send the money on either of those things, I have already stretched myself to get to this point.

 

[bods]

You could put a turbo blanket on and probably even wrap the dump pipe and first section of the exhaust with heat wrap, but I don't think that will help your intake temps at all. The reason being, they are behind the intake and a turbo blanket and heat wrapped piping will make the turbo hold the heat anyway.

The only real option is a snorkel, to help get cooler air into the engine bay. You could probably heat wrap the intake piping from the snorkel to the airbox to stop heat from getting in if you wanted to... providing you get a snorkel fitted. They aren't overly hard to fit yourself, or you could always get help from someone on the forum if you aren't confident doing it yourself...

 

[MattWij]

Yeah not a fan of the thought putting of putting a hole saw into my quarter panel, I do a good job until I get tired or frustrated, and then I just hack stuff together.. hahaha.

I think at this point a snorkel is probably the only thing that will do much. I think $700 was a pretty high quote and the first one I got. I can probably get better.

 

[happy john]

You can do much better than $700 for a snorkel, the main thing is to make sure it's properly sealed.

 

[Black_Outlaw]

Is your intercooler now full of oil from not having a Catch Can installed? I see intake temps around 2.0c above ambient - which was a lot higher before I cleaned out my intercooler / piping.

These YD25 certainly are heavy breathers!

 

[MattWij]

Id does have a catch can, however I'm not convinced it does a good job. I was thinking maby a provent.

Where is the intake temp measured? I figured it would be in the path before the turbo?

 

[Old.Tony]

Intake temp is measured by the MAFS just outside the air filter box.

 

[Black_Outlaw]

Which is what I thought too.. It measures FLOW and Temp..

However, It can take as much a 5 or so minutes to drop intake temps even 1 degree when moving.. and as soon as you come to a stop, the temps rise within 30 seconds..

SO - seeing temps above 50C in a moving car means it must be close on 50C outside, or you have an airleak around the MAFS and it's sucking in and measuring engine bay air..

Yesterday it was 29 here. My intake temps sat on 30 whilst driving, and pushing 6psi - and rose to 39 while stationary at the lights..

50 is extreme.. Perhaps your MAFS is covered in Oil and Soot?

 

[MattWij]

HHmm, the maf is clean, cleaned about 2 months ago. Temp is anywhere between 10*C and 40*C higher than outside unless I have been driving at a good clip without having to stop. I'll inspect the piping, it must be getting in from somewhere. Its fairly common to be at around 45 to 65 intake temp when putting around in 25 degree weather.

 

[Old.Tony]

I've got some driving to do tomorrow, I'll note how bad mine gets in traffic.

 

[MattWij]

Cheers for that, Will be interesting to see.

 

[Old.Tony]

Well the verdict is in. In traffic, and in low speed driving, my coolant temps are around 96C so there's a slightly higher temp in the engine bay. My MAFS is reporting only a couple of degrees above what my ambient sensor is reporting. At 80km/h or more, they're reporting the same temp (as expected).

And that's with my viscous hub (fluid couple) not working properly. I've waited until today to replace it, and that's done, I expect only a minor change around town or at moderate speeds. I do expect it to get a little warmer at Bathurst (going there at Easter, look for my car you should spot it during the races). I'll be staying right behind the pits for the weekend, taking the van up. Expect the hills to be a little nicer this time, temps usually get pretty high towing 2.5T up hill but now I've got a new viscous hub things should be better.

 

[Rabbid-chop]

Engine bay temps will be substantially higher when stationary because of the lack of air-flow apart from what the fan is blowing through the radiator.
At highway speeds, especially in cooler weather when the thermostat isnt wide open, it should get a bit closer to ambient.

 

[Rabbid-chop]

Also, it would be interesting to log temps between the intercooler and the intake manifold.

 

[Old.Tony]

Wouldn't be difficult, drop a thermocouple in before the intercooler, after the intercooler and in the intake manifold so you can see all three figures.

Because Nissan only measure the air temp at the air box, I think they're computing the expected temps at other points in the system. If you compress the air a certain amount the temperature will rise by a given amount depending on the amount of air (hence flow rate is important there). The intercooler can be expected to perform at a certain rate too. Not a perfect system but the variations of a few degrees here or there don't really make a lot of difference when calculating how much fuel is needed at that moment and things like the HO2S in the exhaust can handle the job of determining if there's any air left for the cat.

 

[Tappet]

I think something is wrong with the piping. As far as I can see D40's take the inlet air from between the inner and outer guards. I wouldn't of thought you could see such high I.A. temps. To the point that it affects performance, without something wrong somewhere. Where the tube from the air-box enters the guard there is a foam looking seal. Is that in tact or wasted away? Good place to start anyhow. Next step remove the inner guard and see whats going on in there. With a bit of flexible ducting it wouldn't take much to extend the air pick-up point to a more cooler spot. Say behind the bumper. So long as your not planing to ford any creeks.

A jacket over the turbo would help but that is just trying to get around the problem. Under bonnet temps up in that passenger side are searing, like most modern turbocharged cars and trucks. So certainly wouldn't hurt to do so. Would give other components that live up in the top L/H side of the engine bay an easier time to.

I have thought of putting in a bonnet vent straight above the turbo to get rid of some of that hot air. Ok if your prepared to cut holes in your bonnet. There a ridiculous price and there is cheaper boy racer ones available but these look discrete and factory like. http://www.ebay.com.au/itm/New-AIT-...272066?hash=item35fc9ad482:g:bXsAAOSwNSxVNhTe

I

 

[Rabbid-chop]

Time for an ecu reset maybe if everything else checks out?

 

[Black_Outlaw]

38 here yesterday. IAT went near 48-50 on red lights, slow crawls but always went back down to 38 when driving at steady pace, ususally took about 5-8 minutes. AND - I have no heat shielding

Something is amiss with yours. You're sucking in hot engine bay air from somewhere. As above - check your airbox is sealed well and all connections firm.