Underbonnet temp datalogging

Has anyone here done this, or knows where I can find data on the subject? (mkiv-specific obviously!)

Charge temp datalogging from JSpecs would also be relevant.

I've just went out on an 'exploratory' mission and I am trying to make sense of the data I've got. 25C ambient, 60C the average intake temps off-boost, taking it easy.

That's a lot of feken heatsoak in the bay :thumbdown

TBH john, ive order a temp probe from ebay and im waiting for it to arrive then i'll start datalogging my results. Im also looking to order some heat relective material to cover my FMIC pipes and air filter pipe with, then i can compare how that material will help reduce heat soak. i remember daveburwash from this forum talking about his results not long ago.

also im sure JohnK has some useful info on this subject

If you search I have posted a few times on this subject, under the cone filters are crap type thread.

My research is by no means complete and I have been sidetracked with another project on the car at the moment so am unable to continue testing.

I would be very interested in any info that you get.

yeah, I remember that cone thread.

Looks like you found temps similar to mine, despite having a single. You don't say what the external temps were though, today it was a hot day 25C most of the time.

I went out especially for this, to trace the rate of temp rise, check underbonnet, pressurised intake pre-i/c, throttle body and charge temps.

They are all horrible once the car is up to operating temp (give it 10 mins of mild driving) they were hovering around 57C(off-boost low speed) and 62C (off-boost high speed)

aircon on/off made no difference

Boost made no difference to speak of My charge temp thermocouple is very quick to react, still it didn't bat an eyelid as boost shifted from vacuum to 1.2bar. How queer.

Water injection made no appreciable difference either, apart from eliminating the heatsoak that sits in afterwards:confused:

[remember that I run precompressor injection, so the cooling effects are before the turbos, during compression, on the way to the i/c, after the i/c all the way to the throttle body, and what's left lowers combustion pressure peaks (over 1bar)]

Also note that all my observations were with the car on the move, the SMIC is young and lively, and it benefited from excellent airflow, something not possible on a RR.

The SMIC core temps were much closer to ambient, meaning that it was not the weak link that some people think it is.

I'm gonna look into this closer in the future, as experienced people here will know every 4C of intake air temp rise equals approx 1% power loss (via reduced air density)

I thought that the AFRs of mr "T" were a bad joke but this temp situation is taking the pish

The days when I logged were between 25 and 30c

quite comparable then.

One thing that bugs me is the location of my charge temp sensor (well, the tip of it).

The one I'm using now is not meant to be directly in the airstream as you'd think, rather be hooked in one of the boost signal pipes branching off the throttle body (like the boost gauge does)

I tried to keep it as close to the main stream as possible, but it still sits in a 'dead' end, a hose going towards a boost pressure switch. So I'm not sure how quickly the air in that hose is replenished --- but since boost/vacuum is sensed immediately, what the heck, temp would vary as well, wouldn't it?

Unfortunately I didn't have the chance to have these measurements back when I had the Apexi cone filter (the whole week it lasted in my possesion, lol) who knows what the charge temps would have been with that one.

It would be immersed in that 60C environment, what a sad step backwards that would have been...

I was more intested in airbox temps as thats what I am trying to develop as I can no longer fit the stock airbox.

I would be interested in temps inside the stock box and post intercooler temps.

I didn't have a probe inside the stock airbox, but I'd be surprised if it were over ambient+5C max though (air is drawn continously from outside the bay)

The post-intercooler temps without W.I. were ambient+35C even off-boost. Not good.

I agree far too high, I didnt realise you were post intercooler.

You say that the IC core is approx ambient, so what is heating the air between that and where you measured? The probe is freely in air, not touching anything else giving a false reading?

I data-logged whilst running at Bovingdon.

Under-bonnet ambient temp once I'd warmed up were 57degs IIRC. As I hooned with all my little stock twin, stock IC might, at 16psi, over the 1/8th the temp dropped down to 56degs. I got up to 87mph in just under 10 secs. (All from memory, and approximate!)

I can e-mail the excel file, but it's 8MB (8 Channels logging at 100Hz, and 8 channels at 50Hz for about 3 minutes IIRC) OR if you've got the AEM logging softare, I seem to remember if being about 250KB or something like that.

Tony's figures are in similar ballpark then, Bovington day was a tad cooler than today, and it rained a bit, so 3-4C lower is to be expected.

But feck me, the temps we're talking are SciFi

My main thermocouple is made especially for motorsport use, it is already in a 'shell' which you seal within the boost hoses. It is not a wire sticking through the boost pipe.

I've changed the pickup point of the sensor signal, from the MAP/FPR to the one right beside it:

http://www.max-boost.co.uk/stuff/new_boost_pipe_front.jpg

The only difference is that it hasn't got that little filter in between (or whatever else that blob is)

They are one inch apart.

Temps now appear to be around 5C lower, still a ludicrous ambient+30C.

I really don't get this. With similar intercooling I'd normally get ambient temps at the throttle body, certainly if the car hasn't boosted AT ALL. What is the story with Supra's engine bay?

Only thing off-stock is that I haven't got the engine undertray fitted, but that wouldn't have a dramatic impact on underbonnet temps, surely... Guess I'll have to fit it and verify.

The question remains, what is heating the air up so much?

30C - 35C out of nowhere are worth about 30bhp in my case.

And don't get me started on the silly-billy AFRs from 8psi upwards. That's easily another 30bhp out of the window.

These two could explain a lot of the missing bhp I've been looking for (cue the 'fundamental flaw' thread)

The question remains, what is heating the air up so much?

Two turbos, a restrictive manifold, 6 cylinder block and not a lot of space either side?!

Two turbos, a restrictive manifold, 6 cylinder block and not a lot of space either side?!

The volume of air passing through I wouldnt have thought it would have had time to get that hot.

Two turbos, a restrictive manifold, 6 cylinder block and not a lot of space either side?!

Yeah, it's probably radiated heat, too many hot pipes lying around in a tight bay.

What I find interesting is that driving off-boost at low speeds produces higher temps (by about 3-5C) compared to driving off-boost at higher speeds. In other cars it is the other way round

My view is that this indicates limited airflow inside the supra's bay.

Another interesting observation was that charge temps don't increase with boost, not even at 18psi. Again and again. I was trying to promote extra heatsoak, but nothing (with the car moving, on a RR the lack of airflow through the SMIC might show different results)

Once this massive 'residual' heatsoak settles in then temps stay the same. Such is the thermal mass of the whole structure.

The SMIC is nice and cool all along oblivious to the drama played inside the bay.

It would be interested to have measurements from a soop with a good single installation (thermal blanket etc) and a decent air intake (pickup point at the SMIC cavity)

Also a single with the SMIC and the airbox still in place (althought I doubt anyone has kept the "crappy" and "uncool" stock airbox)

In the light of these -inconclusive- figures I'd think twice (no, trice) before slapping a FMIC in front of that bay.

Maybe it's time to design a massive water/air chargecooler for the supra, siting the water rad where the SMIC normally sits?

I looked at charge cooling a few years ago, before going with the fmic.One big advantage is that the charge cooler can sit between the rad and engine resulting is very short IC pipework(and far less volume) resulting in less lag.

In your case Charlie chargecooling would be even easier to fit, because you have forgone your aircon (I wouldn't do that!)

Soooooo you could use the stock aircon condenser as the chargecooler water rad. It is in a kickass location, ducted and everything already from the factory, with lots of internal volume to cover the needs of a high-boost supra.

The SMIC cavity could then be left available for a decent air intake.

The water/air cores could replace the stock SMIC--->intake pipes, keeping the path clean and efficient.

Best of all worlds, except the cabin temps with a black car in the summer

That's my vision of a supra chargecooler, anyway....

A fellow in supraforums had a good idea --- I wonder how I didn't pick it up myself, doh...

The post-SMIC pipe passes just after the coolant rad, and especially with the undertray in place the hot air from the rads has no option but to preheat that pipe.

Which is long and black, surely it doesn't do the charge temps any good.

I will shield the pipe from this heat and see if the difference is worth the aggro. Even 3-4C lowering of the charge temps will be worth 3-4bhp and increased reliability.

Fingers crossed.

I know the pipe you mean, it looks quite thick though and that plastic isnt a bad thermal insulator. I look forward to your results.

Every day I watch the charge temps start from the exact level as ambient, and move upwards minute by minute. After less than 10mins they are 30-35C over ambient without being on-boost even *once*

This pattern is consistent every time.

Even a drop of 2-3C will be clearly measurable, they have never been less than ambient+30C

Is your WI just injecting pre-turbo, or have you got another injection point as well?

I've recently installed a WI in my rex (diff motor I know, but still runs very hot, especially with tiny stock intercooler), injecting just after intercooler and near the throttle body and the effect of charge temps has been great. Its boost activated, and after a run on boost you watch the charge temps drop...where as before I would quickly get into a heat soak situation.

I think if your just injecting pre-turbo, you will have improved the efficiency of the turbos (someone went into the dynamics of it once and said how it can shift it from an abiatic reaction to a near isothermal one), but the effect of charge temps with SMIC still in place will be limited since the cooled air will be heated up again, as all the water spray would have been atomised in the turbos. If you were to run another injector somewhere along the inlet tract I reckon that would have a much more noticeable effect on charge temps, certainly did with mine. Literally drop between 4-8 degrees after a boost, very noticeable in constant on/off boost situations like track/fast road.

I have been told multi-point water injection is the way to go, I need to do what you've done now and set-up pre-compressor injection.

Sorry if ive misread something in this thread and its all been said before...im a bit tired and kind of skim read it

oh, the other day cruising home at night, just boosting enough to get the water flowing, temps went down to 17 degrees