HAI - what's the best temp?
 

I finally fabbed my heat shield for my HAI yesterday and was at 154*F at 60mph on a 4 hour trip on the interstate.

In the city, I watched as IAT climbed to 178 and even 181*F for a breif moment, but it seems city it's going to average high 170's. Is this best? Is it too much? Should I be shooting for 180*F?

This is in my Saturn SL2 auto.

I blocked off the old IAT tube, cut a hole in the airbox and route ONLY hot air in off the manifold, relocated the IAT sensor to the top of the airbox lid so that it reads very accurately. Using SG to view temps.

PS: I do not mind the reduced power, and yes... you notice it at 170*F for sure.

Sorry if this thread and others like it have already been addressed... I'm really looking for "lovemysan" and/or "cheapybob" to chime in here, or other Saturn owners w/ HAI experience.

Oh yeah... check my gas log for my trip results!! :D

WOW!!! your gas mileage went up tremendously.

IMO I would think that as long as your engine doesn't overheat then you are good on the temps. I don't have a saturn but just keep an eye on your coolant temps too. (the scangauge does this well too).

I don't know if you have looked into a grill block but that could help you even more. I think you have made a huge difference in your FE just from the WAI and the scangauge. I remember you saying at one time that your goal was 30MPG. time to raise the bar a little.

Well, to be honest, that was my first ALL HIGHWAY mileage recorded in about a year and a half. I rarely take my car on trips as my g/f loves her Grand Prix w/ all it's add-on's and comforts.

I was expecting 35-36 mpg... like I said somewhere else (Gas saver's w/ record tanks thread) I recalculated the mileage like 5 times and nearly fainted when I was looking at 43 mpg... added the HAI heat shield Sunday morning and SG reported 47.2mpg on the trip home, but I'm going to add some city to it before filling up.

Thanks for the kind words!

I got grill block material from my Dad when I was home over the weekend, it's about 1/8" thick rubber matting. I figured it would hold up to the elements nicely, but I'm not sure it will stretch and hold it's shape and not deform under the pressures of 60mph.

Might be taking the car on a 640mile trip (one way... roughly 1,300 miles total) next week to SC. So my average is going to be way up if I keep reporting 40+.

I must say, I didn't think it was possible... now I'm thinking ANYTHING is possible.

Considering the way you drove to Cleveland vs city driving, your mileage is not surprising in the least. I think attributing any of your fuel economy gain from your previous tank to the HAI is unrealistic.

I'm not sure I follow you... before the HAI and SG I couldn't get past 28mpg w/ city driving, now I keep getting 31.xx.

I always have tires at sidewall or a bit higher, but for the trip I aired to 50psi cold, which means, probably 55 psi after warming up. I never use A/C in city, and although I cannot draft much (or at least, it's not very helpful) I coast often, and use neutral when coming to a light. GPH in gear is about 0.48, in neutral it's 0.34.

I'm not saying you're doing anything wrong with your city or highway driving. But i don't see anything in the numbers to suggest that the HAI has improved your fuel economy. Your driving style is pushing both numbers way above epa which is great but the difference between those 2 tanks can't be attributed to the HAI. Your highway mileage with the HAI is 38% higher than your city mileage before the HAI. The EPA highway mileage for your car is 43% higher than city. If anything the HAI has hurt your mileage despite your best efforts.

I'm following you, but it a chasing-my-own-tail kind of way... hehe

I believe I couldn't have done it w/o the HAI... and the fact that it was 43.xx on the way there, then I added the heat shield and got 46.xx on the way back, even though ambient temp was about 14*F higher, it points to one possibility in my eyes... the HAI.

You had a passenger on the way to the airport and I assume you dropped them off and drove back alone. 1 passenger plus luggage can easily account for the 7% difference.

No airport involved in this thread...

I drove there w/ girlfriend and luggage.

Drove back w/ girlfriend and same luggage, plus extra items we purchased and some items my parent's have been complaining I needed to get out of their way since I moved out 3 years ago and left it all there. Probably about 60 lbs extra on the return trip.


So really, more weight on the return trip, higher ambient temps, and average speed of 60mph vs. 57mph on the trip there.

I think that is pretty revealing of the HAI heat shield.

I thought that warmer ambient temps generally equal better fuel economy?
(aside from running AC or rolling the windows down)

No, it just doesn't add up. Hot air intake means lower fuel economy.

warmer air equals less dense air, thus less oxygen. less oxygen equals less fuel to burn said oxygen. less power but less fuel burned.

the decrease in power means that you need more gas to achieve the power needed but if the power isn't needed then less gas overall.

air expands when hot so there is less of it per a given volume at higher temps vs lower temps.

given this, your GPM at idle should be less with warmer air. also at a given throttle position, your GPM should be less. you will need more throttle to give you the same power like for climbing hills or acceleration but all other situations, you will use less gas.

the exception is if your vehicle doesn't take into account the air temp. and even then it may compensate by using the oxy sensor.

just my opinion.

The time taken to pick apart someone else's scientific method could have been used drilling holes and mounting your own HAI, for your own "perfect unbiased trials." I will add that before summer hit my mileage went up with HAI. I ran 4 1/2 tanks with that as the only piece i changed. I never moved my sensor so as soon as these 100 degree days hit i was pinging like crazy. Now that its moved the car behaves normally. To take full advantage of HAI you have to make sure the sensor is as accurate as possible, or your timing curves are wrong and you can have potential engine damage and lack power unless you spend the $$ for premium fuel. The ecu is as much your friend as it is your foe.

Afterthought: I see a HAI not helping much if you do lots of city driving and are constantly trying to accelerate. More tq down low helps your economy and really isnt needed at flat steady rpm's.

For aggressive city driving without hypermiling strategies, maybe. For highway driving or decent city driving (coasting, DFCO, P&G), not at all. Apart from that, weight has little effect. The bigger reason lighter models get better mileage is because they can come with less power and/or taller gears.

That runs counter to the experience of many users here, who have observed long-term increases attributable to their HAI.

Nope, it means that you need more throttle opening, not more fuel. Wider throttle openings are more efficient, if we assume the same amount of power produced (which is the case in this context).

Okay, thanks everyone...

I'm still hoping to see a few people suggesting the best temperature... I could still tighted tolerances w/ my HAI to increase temp if necessary, or cut a few holes to decrease temps!

Suggestions?

The power loss can be fuel dumping or knock retard. A Scangauge will show both.

My GM 3800 Series II fuel economy is best at 100*F though anything from 80*F to 130*F is just fine. Optimum temps of 70*F to 100*F have shown up in other posts. Unfortunately the temperature is engine dependent which is why you need the Scangauge.

My WAI only requires me move a single piece of duct tape to vary the temperature.

So this means you came back with a different and lighter girlfriend. Clever, but not clever enough to avoid getting caught. :rolleyes:

Too hot or too cold means lower fuel economy. Everyone complains about "winter" mileage. The trick is to get the right amount of heat.

project84,

back to the original question, I have heard that 180 is a good place to be and that 200 is too much. mine without any adjustment to the physical unit will fluctuate from 130 to 179 (being my highest ever). this is just with temp changes in the day. if you set it up to run 180 all the time then your hot days may see 200 or better which isn't good (well from what I have heard).

I'd say to give lovemysan an PM and see what he says. the whole purpose of this thread was to get his opinion anyway.

Consider this, in Phoenix Arizona the record temperature is something like 137 degrees F.

A car must pass emissions under these conditions, and I would think there is some reserve above that temp.

I have no way of confirming that with a scan guage (wish I did, but my car is OBD1).

My VX also has no knock sensor (read that on this forum), but I have never heard my engine ping on the cheapest gas I can buy.

Last winter with my DelSol it took 4 miles for the engine to warm up without a grille block. I never reversed the air intake (my simple WAI) on the Del Sol, but with the grille block it warmed up in 1.5 miles, with outside temps around 32 F.

For those with a scanguage the feedback is virtually instantaneous. In my case its fillup to fillup.

It seems to me that the difference is about 10-15% (fuel economy) and the max temp should not exceed 150F. Of course when it is 100 degrees the difference will be negligible. I tried reversing mine back to its normal position this summer and got the worst mileage in the last couple months, so in my case it seems to make a difference even in the summer.

That doesn't mean I am saying anyone is wrong, it just means that this is what I have observed. I would think the max temp would vary considerably from one car to another.

From 32 degrees to 200 degrees farenheit atmospheric density drops 20%.


There seems to be a lot of concern about WAI causing the engine to run hot. I dont think it will happen, if your cooling system is in good shape. It might happen if you completely block any airflow to the engine compartment. Even then it would be very hard to completely trap all the heat in the engine compartment and an electric cooling fan would run as long as it took to keep the engine cool. Most of your cooling systems heat removal work is due to combustion temps of over 3000 degrees not intake temperatures.

I like my simple intake snorkel reversal route to WAI because it allows the engine to breathe cooler air if you are at higher throttle openings, so when you need emergency power the volume of air entering the engine would also mean the air was cooler than at lower volumes, so you have better power when it is needed, even though I may never use that kind of power.

regards
gary

I have heard it observed that motors run cooler with HAI, for a given RPM, this would be due a smaller amount of charge not making so much heat. I think also less work is done in the compression phase.

Edit: BTW, "Cold Air Intakes" primarily benefit FE when they "get one over" on the ECU by introducing more air than it thinks it's getting. That and reduced pumping loss from a freer flowing intake can help.

Pics of my HAI can now be viewed in my garage.

Hot intake air causes the combustion chamber to run hot. That is different than making the coolant temperature hot which is mostly a function of ignition timing.

For every 10 degrees you increase IAT, you increase the octane requirements by .5.

You also increase the chance for knock which we all know kills your FE not to mention engine life.

I personally refuse to run a WAI because I don't believe the tradeoff for engine wear is worth it. Also, I have a tiny 1.5 engine, any less power would make the car a chore to drive.

I've been running 86 or 87 octane since day own of ownership of my SL2. Had the HAI on about a month and haven't heard any new noises or experienced anything of than a slight reduction in power above 150*F. To compensate, I do as directed by others, wide throttle in highest gear, seems in 3rd gear I can accelerate w/ TPS at 25% and the MPG reading dips to 20's, but in 4th I can go 50% TPS and MPG is still above 30 (speed is the biggest factor there obviously too).

For now, the HAI is my new best friend.

Before HAI the IAT was basically ambient... so I've doubled it in some cases, say from 80*F to 160*F, meaning you suggest I should put in 90 or 91 octane over 87?

Would I benefit in FE for doing so, or is it just to prevent knock/ping?

if your compression ratio is really low though, you don't even need 87 though it is the lowest that you can buy. I think you only need 93 when the compression ratio approaches 12:1 or so. I have seen cars that have a compression ratio of 9 or 8:1 so if you fall into this category, I don't see where it would be an issue. you may require a higher octane but you still may need a minimum of less than 87 which is the lowest you can buy.

this is just my understanding of it.

*edit* BTW, project84, your pics look similar to mine. are you plugging the other end of the tube though. is it some sort of check valve?

The plug that you see isn't really a plug, it's just metal flashing riveted over the hole. That is where the OEM intake air tube was which contained the IATS. Since I relocated the sensor, I got rid of the provisioning as well.

My LT1 Camaro has a compression ratio of 10.5:1 and it requires premium, anything less and it runs like poo.

I want to say the SL2's are 9.5:1

I know that my truck ('04 dakota 4.7L) is 9 even.

not sure about the car

My '93 SL2 would ping pretty fiercely in low rpm/high throttle conditions. It ran much smoother with 93 octane, for sure. It was a stick shift so I may have been lugging it a bit...

Not sure that car was considered "high compression" or not.

A technical note on comment #22 by Project84. 80*F to 160*F is not doubling the temperature. Anything having to do with thermodynamics, including ideal gas law equation, is based on absolute zero. 80*F to 16*F is really 540*K (Kelvin) to 620*K, a 15% increase.

Running a HAI may not be the best way to improve economy IMO. All I see it doing is making the IAT sensor read higher so that the fuel maps are leaned off via the temp compesation tables in the engine management system.

The better way would be to have a cold air intake and just to lean off the fuel mixture. Sometimes just turning the fuel pressure regulator down a little can achieve this.

Whilst hot air is of some benefit to making the fuel atomise better in the cylinder, depending on the where the fuel rail is positioned on the engine, if the fuel rail gets little heat then warming up the fuel can help a little.

In summary, I think only a small percentage of the fuel economy gain is from the heat. I think a majority is just from throwing less fuel into the cylinder which can be done via other methods. The main one being programable engine management systems.

For me, it's really as simple as this...

Total cost for HAI build - $14

Total saved in less than a month.... and I only drive about 700 miles per month... projected near $25.

Whether I'm getting the gain from here or there, I NEVER got above 27 in mixed driving in the 3 years of owning my SL2. I put the HAI on and WHAMO 31.xx 4 consecutive times.

My best highway mpg was 33... My new best? 46.

I'm an instantaneous kind of guy, whether the engine blows up in 5k miles due to this or not, I don't honestly care (good excuse to do the SOHC 5sp swap). I modded the car, am seeing amazing results, and I couldn't be happier.

I'm happier if I get some of these results and possibly modding my wife's car too.. haha

...why would there be these temp compensation tables that lean off the fuel maps? probably because the manufacturers think hot air is less dense air.

It causes the compression before the spark to be hotter which will increase octane requirements. After the spark running hot has little to do with the IAT unless the IAT has some secondary benefit.

You have air temp compensation maps in most EMS. When air is cold it is more dense and needs more fuel and visa versa, when its hotter it needs less fuel. You program air temp comp so the car runs more uniformly between hot and cold climates. Its not easy to get it to run consistenly bewteen the extremes but the manufacturers do it quite well.
But if you are introducing 100deg air into the air intake you would be leaning the maps to the maximum.

There are even fuel temp comp maps

I don't think they are on cars anymore, but my 1981 Buick has a barometric pressure sensor. I guess its to modify the mixture for high altitudes. Doesn't seem to do a good job though, because when I drive it in the mountains it runs like crap, and the check engine light usually comes on.

-Jay

I have not yet modified my 96 Saturn SC1, but I took two road trips this year to Arizona and in March I averaged 45 MPG and in June (with temps in the 100's) I averaged 49 MPG so I am pretty sure that HAI is the way to go. I am saving up my pennies (if I get impatient I may sell plasma too) for a Scangauge, because there will never be an answer to the general question of what's the best intake temperature. The best temperature is the one that works best for you and your car. This can only be determined through experimentation and you will need good instrumentation to nail it. I think the hardest part will be building a device to keep the temperature constant.

Good luck to you 96sc1... I'm jealous of your SOHC engine!!

Been looking for a LONG time for an '01-'02 SC1 5sp in good shape w/ less than 100k for a reasonable price w/ no luck... :(

If you let it go over 200f you will see mpg drop as ignition retards probably due to ping. I like 175f to 180f. That seems to give best results on my SC1.

Funny how people argue with things that actually work, huh? Actual results are what counts, IMO.

When you build it, start with the intake input 1" from the header. I heard a remote sensing oven thermometer with the probe in the airbox works, if you don't want to splurge for the scangage. Since your car has the same motor as mine, I'd guess my 175f to 180f in the airbox should also work for yours.

Sorry, I don't think it "leans" it if the air is heated because the system will sense less oxygen and inject less fuel to match it. The maps are designed to handle up to 247f, but from my experience, hotter than 200f seems to cause ignition retard and abnormal loss of power.

If she doesn't have the supercharged Grand Prix, I bet a hot air intake would work on it, too, LOL.