LT1 intake air temperature question

Guys, those that can read this from their computers at hot idle with the hood up, what kind of IAT temperatures are you getting?

Long story short, we all know I've been through all kinds of hell with misfires when I put in a new motor last year, and chasing my tail on all kinds of components and even lost that motor over running with those misfires too long. I've done an opti job a couple of times, swapped out ICMs/Coils, re-done all of the plug wires, new plugs, etc. I thought I had this nipped in the bud at TWS, but then again I only made 5-6 laps at 50% pace before I popped the motor.

Yesterday on the dyno the car with a fresh new motor, new plugs/wires, freshly cleaned injectors, it again started breaking up above 5k RPMs after a couple of pulls. Instinctively I remember some comments that were made about my aluminum intake elbow, which was put in with the new motor last year; it was piping hot to the touch. It would break up above 120-125*F IAT. We put a small fan right on it, and then were able to get the IATs much lower and make 6-7 back to back pulls with no problem with the oil/water temps going up as expected.

Went home, couldn't find my old plastic/rubber piece, so I insulated and wrapped the hell out of it with 15ft of gold tape. I saw an improvement in IAT and the elbow is now just warm to the touch, but it will still 110-115*F at idle. (90*F outside, probably 100*F in my garage, coolant at 195-200).

Later on I found and put on a stock plastic elbow, and was getting 115*F-120*F at idle compared to my super insulated metal elbow; so it actually was a little worse.

I then punched a small hole in the plastic assembly right after the filter and put in a second IAT sensor there and moved the wire over to it, IATs readings are now down to 100-105*F, the starting temps under which I was able to get solid pulls. Yes I know this actually is just fooling the computer, just wanted to see if it would sound less rich at idle and decel, and it does so for longer now.

I think I may be good now, but to be safe I'm getting some more gold wrap and insulation, and a heat shield for the air filter. I will likely re-dyno later this week to make sure this all works before I go to Hallett.

The only other issue I can think of is I'm picking up a lot of heat from the oil cooler/lines that are near/below the filter. Attached are pictures of everything I just talked about. Those of you not familiar with the LT1s note that the elbow/TB is right above the waterpump/neck, and the stock IAT sensor location is right in it.

Can you guys with running LT1s and scanners see what your IATs are at hot idle with the hood up?

Wondering if I have just been cooking my air filter the entire time or if something else is wrong with the system that is causing it to react so poorly to higher IATs.

I can't get images to work, just click here and scroll down:

http://imgur.com/a/tMuVE

I see your problem..... Your feeding hot air off the oil cooler right to the air filter and the air filter is also pulling hot engine bay air into it as well.
You need to run a 100% stock set-up. The stock set-up pulls air from in front of the core support. You also now know why my oil cooler is on the passenger side. It was just the best place for it.

Yeah, you're right. I've got an IAT issue, I could try to bandaid it with more wrap and heatshielding, but in reality I've got a big source of heat too close to the filter.

Already started pulling the cooler lines off, waiting for some more hose to come in so I can run it to the other side.

Found all my stock intake parts. Just going to wrap it all up to be safe.

One more thing I can't believe I forgot to mention.

Morning after the dyno I got to work on the intake swapping and testing, and got the motor nice and warm in my corner of the garage. It was 90* outside but with little ventilation I'm sure ambient temp near the front of the car against the wall was close to 100*F. Needless to say things were toasting, but the car should be able to handle it at idle as it always has.

Anyways suddenly the car started stalling and dying, in some cases attempting to restart would cause backfiring thru the intake, and it refused to start. No codes as usual. Went out for lunch and let the car cool off for a couple hours, started right back up, once it got warm it started acting up again. With it hot I swapped out the ICM and it fixed it right up, has been starting up and staying running while hot since.

Took a close look at it and there's a big crack in the plastic case near the connector.

So I'll be going back to the dyno with an all stock intake wrapped with gold tape, relocated oil cooler, and a replaced ICM. This better work or I'm throwing in the towel for Hallett.

wow, what an incredibly frustrating collection of problems. Good look man.

Thanks, it's the right combination of bad luck, bad decisions, and everything that goes with building a race car for the first time.

I've got a spare MAP sensor too, may throw that on just in case those back fires cooked it...

Moved the oil cooler to the other side of the car. Wish I did this sooner as I can set it further back with the way the inner fender is (favorably) shaped on that side.

Got a new intake elbow and stock airbox/pipe/snorkel in place along with a brand new delco ICM; turns out the replacement and the one that broke were both for a '93, not a '96. Instead of 10-11 degrees of advance at idle with the wrong ICMs I now get 15-16 degrees at idle, could make a difference.

At idle now I'm getting like 105*F at idle in the stock sensor location, about 100*F in the airbox; airbox actually cools off more than the elbow when I blip the throttle. I will dyno with the stock location sensor and switch over to the airbox location if I still have issues. Compare this to starting temps of 115*F with the wrapped aluminum...

Went to the dyno today without calling in advance (they said Friday was OK earleir in the week). They had issues with a customer's car stuck on the dyno and sent me home; going back on Monday for almost no charge for the inconvenience. Kind of a blessing in disguise because I still need to finish the rest of the car (nuts/bolts/clamps etc).

I was hoping to dyno with an unwrapped plastic intake to see what happens first; will go ahead and just wrap this one to get the IATs down further.

As long as I can make pulls withou misfires again I'll be clear for Hallett!

Between the last dyno and today's dyno:

1. Diagnosed/replaced busted ICM model, that turned also out to be from the wrong year range
2. Found no-so-great upper/lower/IAC throttle body sealing, fixed that too
3. Plugs were partially fouled and indicative of retarded timing.
4. Moved oil cooler to other side, swapped back to 100% stock intake plastic and gold wrapped elbow to be safe.
5. Swapped my NGK TR55s gapped at 0.055 to TR6s gapped at .045 (LT1 spec is 0.050). Never had an issue with TR55s with the first motor, but figured a tighter gap could only help when I've had constant issues with retarding/losing spark.

Swapping the ICM netted me an improvement from 10-11* of timing advance to 15-16* at idle. Swapping the plugs, fixing the TB gaskets, and re-setting the rockers netted me another 4-5* of advance to 20-21*, where it should be, and a slight bump in vacuum idle up to the 20mm/hg I remember having for the longest time.

Seeing the numbers and hearing the car start/idle had me feeling pretty confident. Dyno operator commented that the car started and idled way better than last time so it wasn't in my head.

Re-ran the dyno, saw that IATs were in the 105*F range at WOT, used to be 125*F. No misfires, pulled nice and strong for 7 pulls without the help of a fan this time. A/F ratio was right on the money via wideband.

I'm happy. Now to finish buttoning up the rest of the car...

Need to add a Like button for your last update. Congrats man! Good job getting it all sorted it out. I was rooting for you :)

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Originally Posted by Pranav

I'm happy. Now to finish buttoning up the rest of the car...

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You know this means you cannot blame the car. Given your thoughtful troubleshooting process it makes me wonder how I ever make an event.

Intra-class "manties" for any RR shod car finishing behind old, tired, and slow RA1 runners?

Quote:

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Originally Posted by Fbody383

You know this means you cannot blame the car. Given your thoughtful troubleshooting process it makes me wonder how I ever make an event.

Intra-class "manties" for any RR shod car finishing behind old, tired, and slow RA1 runners?

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Do we have any proof the RR is faster? I know it does not last as long (or at least at TWS I was not impressed with the tire life of the RR's). I know TWS is hard on tires but if the RR is so much faster I would have thought we would have seen new track records. I'm not saying the RR is not faster (I certainly don't know) I'm just wondering if we have proof that it is?

JJ

Quote:

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Originally Posted by Fbody383

Given your thoughtful troubleshooting process it makes me wonder how I ever make an event.

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I'm spoiled by the OBD2 port. Without it I'd still be lost as hell.

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Originally Posted by ShadowBolt

Do we have any proof the RR is faster? I know it does not last as long (or at least at TWS I was not impressed with the tire life of the RR's). I know TWS is hard on tires but if the RR is so much faster I would have thought we would have seen new track records. I'm not saying the RR is not faster (I certainly don't know) I'm just wondering if we have proof that it is?

JJ

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Let's swap tires at Hallett and see.

Quote:

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Originally Posted by Fbody383

Let's swap tires at Hallett and see.

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Okay. My 888's for your RA1's.

Works for me.

JJ

Quote:

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Originally Posted by ShadowBolt

Do we have any proof the RR is faster? I know it does not last as long (or at least at TWS I was not impressed with the tire life of the RR's). I know TWS is hard on tires but if the RR is so much faster I would have thought we would have seen new track records. I'm not saying the RR is not faster (I certainly don't know) I'm just wondering if we have proof that it is?

JJ

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I'm happy with the RR wear after TWS, you have to baby them though, can't be driving like a sprint car

I ran RA1's on a Saturday and RR's on a Sunday during a DE a month or so ago. Conditions were similar both days, and my best lap time Saturday with RA1's was 1:56.6 with an optimal of 1:55.8. Sunday with the RR's best time was a 1:55.4 and optimal of 1:54.7. The traffic was pretty shitty both days so it was hard to get clean laps.

This was the weekend after the TWS race. A cool front came through along with some rain in between the DE and race weekend, so the weather for the DE was pretty much perfect in the mornings. The weather for our TWS race weekend wasn't as good as it was at the April 2013 event either, that's why I think the lap times didn't see an improvement. The Spec Miatas didn't see an improvement in lap times from the previous year either, but they claim the RR's are about 1 second faster.

There are a number of variables that could have contributed to the differences in lap times between Saturday and Sunday though. I don't think weather was much of a factor. My lines and braking zones were pretty consistent both days, but it's definitely plausible that I improved by 1.0+ second over the course of weekend. If I had a better understanding of what to look at in the data I could probably figure out where I was losing time, and whether it was due to the tires and/or my driving. After talking with a SM buddy of mine, he was saying that the max G's the tires can handle are similar, but the RR's can be held at the limit better than the RA1's, which allows for higher sustained G's, which means a higher average speed through the corner. What was interesting is that he said max G's under braking for both tires were similar. If I can remember I'll take another look at the data and see what I can figure out.

What coolant temps did all you 4th gen LT1 guys see this weekend? Need help rationalizing something while it's still fresh in memory.

Was pushing mid/high 230s all during the races on Saturday. My gauge in the cylinder head would shoot up to at/above 250 and push a little water out the overflow when I shut it off without letting it cool off a little longer at idle, but other than that I wasn't losing any water on track (running the higher pressure cap).

Only changes to my cooling system were:
1. Converting steam pipes to better flowing AN hose
2. Finished improving/sealing rad ducting
3. One step higher in heat range plugs (colder plug, more heat extraction from chamber into heads):

Quote:

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Originally Posted by Pranav

5. Swapped my NGK TR55s gapped at 0.055 to TR6s gapped at .045 (LT1 spec is 0.050). Never had an issue with TR55s with the first motor, but figured a tighter gap could only help when I've had constant issues with retarding/losing spark.

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The plugs came out looking much better, but in hindsight I don't believe there was any need to go colder on plugs, just adjust the gap on what I had to help reduce any chance of losing spark. Anyone play around with heat ranges and notice differences in coolant temp?

The only other things that are suspect are:
1. Possibility of dam folding back; running a stock piece plus an extension
2. I have a fine mesh on the inlet between the core support and bumper support; I've been told taking that out and covering the radiator in mesh instead could improve airflow to radiator.
3. Brake ducts integrated into airdam; I taped 50% of them off between race 1 and race 2. I think I saw an improvement by a few degrees, not sure, but second race's ambient temps were higher I think.
4. Have not notched or cut up bumper support to let in more air yet.

Planning on relocating brake ducts and throwing everything I have at radiator ducting before beating on the car this summer, but wanted to see if going back to a stock heat range is a good idea. Plugs looked very clean with but with a solid black fuel ring, absolutely no misfires this weekend. My memory seems to tell me that I idled and dynoed higher coolant temps with the "colder" plugs, but it may be in my head...

This may be obvious, but make sure the fins on the radiator are clean. I'm always amazed at how much crap I can get out from in between those fins. I cleaned mine out after 5 weekends and there was a lot more rubber and grass in there than I would've expected for that short of time.

They are spotless; I've got the fine mesh covering up the entire inlet leading to the radiator, was cleaning that out between races.

On the motor #1 I ran unprotected and got all kinds of dings and crap in the radiator fins; had a shop clean all of the fins out and straighten them all before running motor #2, which ran fairly cool (215-220 max) but that was ECR, MSRH, and MSRC. This is my first actual "hot" event since motor #1 (which had all kinds of cooling issues).

Quote:

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Originally Posted by Pranav

What coolant temps did all you 4th gen LT1 guys see this weekend? Need help rationalizing something while it's still fresh in memory

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High; the needle was vertical and touching that orange mark in the gauge - in my car I figure it just means to keep going.

Seriously though, it was hot but the gauge would start moving down within a couple of corners on the cool down lap and the PCM never went into limp mode. I don't recall seeing any steam and I believe Scott check the water Sunday morning and it was full.

No idea on oil temps but I'm pretty sure it will be black when I change it.

Good to hear. I had thought you were running lower than that but may have confused your experience with someone else's.

I had my oil temp warning set to 270*F; after the first race I bumped it up to 300*F; quick checks showed I never got above 280*F (it doesn't display temp unless I switch pages on the dash). I haven't even fully ducted my oil cooler yet :D

I've got the mesh in front of mine and still had a bunch of crap get in the fins. One other thing to think about is the finer the mesh the less surface area you have for air to enter.

8 weekends ago, right after Hallet:

-Fill tank up with Sta-bil additive
-Pulled/checked another oil filter, came back clean
-Extended idle test (to let sta-bil circulate), all is good in the hood with no codes/misfires/noises
-Fill car up with junk and park it

This weekend I get the car running and put it up on stands to start on my list of stuff to do/cleanup on the car...

After a while, once the car warmed up, I noticed an erratic tap tap tap coming from the exhaust pipe, a little while later I get a code for misfire cylinder #7.

Since I was going to go ahead and switch back to stock heat range plugs (ran one step colder as part of previous issue's diagnostic, turned out unnecessary), I went ahead and pulled the plug on this cylinder. It looked fine so I put a stock heat range plug back in and fired it up.

Still had the erratic tap tap tap coming from the exhaust but it seemed to have decreased, if I revved it up to 2-3k RPMs then let off back to idle, it would go away for a while (at idle), but then come back.

I pull the #7 injector plug with it running and the tapping becomes constant. Putting that one back in and started pulling random injector plug wires. On each of the others, if I pulled the plug the frequency of the tap tap tap would increase, but not become constant like it did on #7.

Next I lifted the fuel rail off the intake so the injector ends were out, then cranked it. None of the injectors were leaking when closed, but I really could not tell much by the spray patterns when each one opened. I want to say the driver's side (where #7 is) was weaker, but can't tell.

Finally all through this I began watching long term fuel trim. Bank 1 (where #7 is, driver's side) was initially at +9%, bank 2 at around +2-3%. Not sure if these numbers are of concern or not.

In the end after messing with the spark plug and injectors, I did a reset and ran it again, it seemed to have decreased in frequency and the bank 1 long term fuel trim went down to +5% with bank 2 still at +2-3%.

It started getting late so I could not do any further diagnostic, nor leave it idling too long (#7 misfire code hadn't come back yet), but the popping/tapping out the exhaust remained in lesser intensity.

Went ahead and pulled the injectors and will have them checked again this week while I'm away from the car until the weekend.

Things to note:
- #7 is the last injector to get fuel before it goes to the regulator/return
- Before I ever fired up the new motor, I had the fuel rails and injectors cleaned, replumbed everything from the pump to the rails with 6AN PTFE and a 1 micron canton filter
-Could not see any burn marks or issues with #7 plug wire, forgot to ohm/check it further before running out of time. Will check this weekend.

Here I was thinking I'd just have a simple to do list with nothing new to fix. Sounds like the car is punishing me for being away from it for so long.

I'll be asking some more questions if the injectors come back OK...

Called the injector shop. They said they all needed a cleaning but were not "problematic." #7 was "fine" and i'll get my hands on the numbers later today or tomorrow when I pick them up.

My suspicion is that I didnt clean out the supply line well out enough after cutting the hoses with the chop saw, not big stuff.

What on earth else can go wrong from the car sitting for 8 weeks for it to start misfiring one cylinder?

I'll be checking plug wires and figure out how to check compression in that tight space as next steps along with the (planned) rechecking/resetting of rockers. Wish I had more time last Sunday to properly check everything out...

If that doesn't pan out, I have a 96 OBD2 setup, how can I scan everything that's going on with injector pulses and misfire counts using my laptop and a obd2 cable? Software to get??? I've been using a normal scanner using a bluetooth adapter and the phone to get limited realtime info and pull codes. Time to get more detailed before I try throwing parts at it...

time to upgrade to an LS1.....and it just so happens we have one with a k-member ready to go for you! ;)

The thought has crossed my mind many times. I feel like I've gone too far down the lt1 rabbit hole to come back out again.

Picked up the injectors, I was told the "dirty" was caused by some black material but no varnish/rust unlike last time. Its the residue from the black metal cutting blade I used to cut the lines. Still waiting on the final flow numbers but I was advised that they weren't anything to worry about, probably <5% loss is my guess.

Car gets fired up this weekend and will see what's next to find and fix is simply putting the injectors back on doesnt do anything. Ordered a spark checker and some long arm heat sleeves so I can get in there and check stuff for real this time. Also will check for bent pushrods while re-checking the rockers.

Being a perfectionist can be frustrating. :D And pay off when you get it right.

Spark testers are now my favorite tool.

#7 plug wire was burned, no way to see until I pulled it out completely.

I had made all new plug wires for the new motor before it went in, looks like the heat sleeve that kept it insulated from the manifold slipped loose.

Back to work...

A leaky plug wire can be quite noisy. You're as thorough as I'd be if I had the energy and fewer projects. For reference to an old/above post, my coolant temps at Hallett (and pretty much everywhere else) were solid at 210 and oil stayed around 275 unless I was up somebody's ass too long, then the coolant would creep to 230 and oil to 300ish. That's why I got the Redline, it can take the heat and not eat my motor. I do have a redneck circle track radiator with integral oil cooler and a coarse screen at the inlet of my bumper.

Lol thanks, part of the persistence comes from not wanting to do another motor swap soon, and just trying to fix things right the first time rather than foolishly throwing parts at it as I've done in the past.

Mine was running at 230-235 no matter what I'd do. Just going to fix the airflow and swap to regular/lower stock heat range plugs and see what happens at NOLA. Think I'll throw it on the dyno one more time to be safe.

Never updated this. So I went and threw it back on the dyno last week to see what it would do after a solid race weekend.

The only thing changed since the last dyno and hallet:
1. Back to stock TR55 plugs, down from the "colder" TR6s I ran at Hallett (went up one step colder in my panic to fix misfires)
2. Fixed burnt plug wire (this didn't cause problems at Hallett, maybe I shifted the insulating shield loose on the tow home or in the garage...)

-A/F ratio was solidly in the 12.5-12.7 range at WOT like it was last time.

-Coolant temps were a bit more stable, last time it got over 220 easily after a few pulls, this time it was around 200-205 after a few pulls, and it was much hotter outside.

-Oil filter came out clean as usual, not a single piece of debris.

I will see what it does at TWS, but it jives with my theory that the colder plugs (more heat transfer to head/water jacket) could've helped elevate my cyl head water temps at Hallett, despite Hallett being Hallett.

http://www.import-car.com/tech-tip-u...ug-heat-range/

So in short, run the stock ****ing plugs if you're running less-than-stock power and compression levels.