95 LT-1 Idle Cell Comparison - Humidity?

[spfautsch]

I've found a Stant 45967 and Gates 33747S that are close, and are shown on another vehicle application that uses the Motorad part (2004 Nissan 2.4L).

The only problem I see with them is they appear to have smaller primary disk openings and the bypass disk stem (on the bottom) is about 2.5mm shorter than the one called for. The Motorad is only about 1mm shorter. This means the bypass may not close completely when the thermostat is open. Probably wouldn't cause any trouble, but I'd prefer the Motorad piece.

[LeMarky Dissod]

I've found a Stant 45967 and Gates 33747S that are close, and are shown on another vehicle application that uses the Motorad part (2004 Nissan 2.4L).
The only problem I see with them is they appear to have smaller primary disk openings and the bypass disk stem (on the bottom) is about 2.5mm shorter than the one called for. The Motorad is only about 1mm shorter.
This means the bypass may not close completely when the thermostat is open. Probably wouldn't cause any trouble, but I'd prefer the Motorad piece.

https://www.z28.com/threads/thermost.../#post-1590316

… The [LT1] thermostat does two things.
The first is to control the coolant coming from the radiator to the pump. The second (the lower disk) cuts off the bypass route that the coolant takes when the thermostat is closed.
When the thermostat is cold/closed, the coolant flows continually through the engine without going to the radiator. That way the thermostat gets an accurate reading.
When the thermostat opens, that path is closed off and all coolant goes through the radiator. Without a thermostat installed, some of the coolant will go back to the engine without going through the radiator.

Besides MotoRad & Stant, I can't think of any other brand names whose thermostats I'd trust.LT1 H2Opumps need LT1 thermostats.

[kur4o]

I've found a Stant 45967 and Gates 33747S that are close, and are shown on another vehicle application that uses the Motorad part (2004 Nissan 2.4L).

The only problem I see with them is they appear to have smaller primary disk openings and the bypass disk stem (on the bottom) is about 2.5mm shorter than the one called for. The Motorad is only about 1mm shorter. This means the bypass may not close completely when the thermostat is open. Probably wouldn't cause any trouble, but I'd prefer the Motorad piece.

Thanks for the part numbers. Does the stock gasket works fine with the 2028?
I also investigate the matter through rockauto and made a list of 2028 interchange part numbers with different open temp and applications. From what I gathered as info, The lT1 thremostat is the same overall dimension as the sbc 94-00 but flows more due to enlarged opening. Too bad delco doesn`t make 170* one.

The main question is, will the 2028 flows enough or should I keep the 160* one and do the cardboard thermostat mod. While searching I also found that the nascar guys target 200-210*F as the best temperature for the combustion process. Completely in par with the most fan settings 100*C-on 95*C-off pre obd2 emission standarts.
Somehow I nailed the temp down with 93*C low and 96*C high.

The reverse flow cooling system might change the Nascar equation and the optimal for lt1 could be 90-93 *C. STill needs experiments to confirm.

For startup test you can always clean the left over fuel with some starter time and injectors fuses off. Nailing down the pedal above 80% tps also stops fuel from being sprayed.

I make some test with hot restarts. First hot restart is always good. Second is almost good and on the third I have long cranking. The test was made with 4-5 seconds run time.

It could be subjective feel but when I adjust the fuel flow constant and return back to stock maf curve, the engine run much much better even though the wideband and spark didn`t show any deviations. I also witness some real low map values.

I dig up 2 logs where 02s flat drop from 50 to 53 *C, than recover with no apparent reason. I know for sure I have other logs too but can`t find them. In par with the EOIT target change from 44 to 56 degrees or 270* to 180* which interpolated is 225*-247.5* at 50-53*C. Really wierd.

[spfautsch]

Thanks for the part numbers. Does the stock gasket works fine with the 2028?

So far so good - it fits around the t-stat housing and I'm not seeing any leaks after 150 miles and about 4 hours of run time. Unfortunately these do not include a new seal so if your current one is getting old I'd suggest getting a new one.

The lT1 thremostat is the same overall dimension as the sbc 94-00 but flows more due to enlarged opening.

This is why I like this particular Motorad part - the advertising on it says it has a 30% larger primary disk from the "standard flow" parts. I also looked at cap pressure and the 6.8L Ford V10 runs at 16 psi also so I guess the only other question is how much bigger is the water pump impeller? Again, I'm happy to be the guinea pig on this one - if it overheats next summer you can rest assured I'll be her complaining about having to replace whatever parts it breaks.

The reverse flow cooling system might change the Nascar equation and the optimal for lt1 could be 90-93 *C.

I've never read the official rules, but I think you may be making a bit of a leap in assuming they're not all running reverse flow cooling. I'm relatively certain I read somewhere that the reverse flow system used by the LT-1 was conceived by Smokey Yunick for just such an application. He was the DaVinci of cheating - err, "skirting the rules".

I dig up 2 logs where 02s flat drop from 50 to 53 *C, than recover with no apparent reason. I know for sure I have other logs too but can`t find them. In par with the EOIT target change from 44 to 56 degrees or 270* to 180* which interpolated is 225*-247.5* at 50-53*C. Really wierd.

Funny you should mention this. I just tested a cold start - ambients here have dropped to -7c and IAT was reading 9.5 in the garage with the door slightly open. Initial start was awful - cranking time was 1.7s. This jumped out as different because I reset BLMs after startup because they were ridiculously high (140s) from the last idle session yesterday. When ECT hit 41.8c right side O2 was reading 36mv steady, and 8 seconds later the left side followed. Idle quality went to crap. I shut it down b/c I wasn't wanting to suffocate on fumes waiting for it to get to operating temp.

[kur4o]

Initial start was awful - cranking time was 1.7s

Is it dumping more fuel or it is starving. IF it needs more, bumping the key several times will do the trick and should start right away on the 2nd to 4th bump.

Decided to look at lt4 calibration to see how the EOIT is set.
The stock settings are

                                      y-LT4 ;y-LT1 ;f-LT1
RESERVED:337A                 fcb $20   20   20
RESERVED:337B                 fcb $20   20   20
RESERVED:337C                 fcb $20   20   20
RESERVED:337D                 fcb $20   20   20
RESERVED:337E                 fcb $20   40   40
RESERVED:337F                 fcb $20   40   40
RESERVED:3380                 fcb $20   40   40
RESERVED:3381                 fcb $30 ; 4c   50
RESERVED:3382                 fcb $40 ; 4e   50
RESERVED:3383                 fcb $50 ; 50   50
RESERVED:3384                 fcb $50 ; 50   50 
RESERVED:3385                 fcb $50 ; 
RESERVED:3386                 fcb $50 ; 
RESERVED:3387                 fcb $50 ; 
RESERVED:3388                 fcb $50 ; 
RESERVED:3389                 fcb $50 ; 
RESERVED:338A                 fcb $50 ;

There is also baro correction applied

RESERVED:338C                 fcb $1D                 ; 1x10 baro correction for EOIT
RESERVED:338C                                         ;
RESERVED:338C                                         ; SOME TABLE RESULT BYTE_EC
RESERVED:338C                                         ; Baro corr to end of inj
RESERVED:338C                                         ; table value-byte_338d=x
RESERVED:338C                                         ; x+end of inj
RESERVED:338D                 fcb $1D
RESERVED:338E                 fcb $1D
RESERVED:338F                 fcb $1D
RESERVED:3390                 fcb $1D
RESERVED:3391                 fcb $1D
RESERVED:3392                 fcb $20
RESERVED:3393                 fcb $20
RESERVED:3394                 fcb $20
RESERVED:3395                 fcb $20

The baro table runs from 53kp to 104.44kp and stock setting are -3 to 0* EOIT added to main EOIT table.
On lt1 and y and f body the baro correction is set to 0.


ANother fueling routine that left untouched and might play big role in blm splits is the transition fueling. There is some alient math there, that substract fuel on certain condition, possible compensation for the fuel left on the walls unevaporated.

[spfautsch]

Is it dumping more fuel or it is starving.

I'm thinking it was starving, but probably not due to a calibration fault. I noticed when I shut it off I could hear the pump running quite a bit longer than usual. It occurred to me this morning it was probably sucking air (the fuel gauge has been reading near E for a day or two). When I peeked in the filler cap I could plainly see the pump's filter sock, and it seems like the pump might have popped out of the bracket. The y-body fuel tank design is one thing GM solidly botched.

After adding a few gallons and re-priming the system, cold start at 6.5c popped right off. So the O2 shift I mentioned on both sides may be invalid due to air in the fuel system.

The stock settings are

My stock bin had this for the 12df2 table:

20
20
20
20
40
40
40
60
60
60
60
60
60
60
60
60
60

There is also baro correction applied

,,,

The baro table runs from 53kp to 104.44kp and stock setting are -3 to 0* EOIT added to main EOIT table.
On lt1 and y and f body the baro correction is set to 0.

Very interesting find.

There is some alient math there, that substract fuel on certain condition, possible compensation for the fuel left on the walls unevaporated.

This is referred to as Tau in the Banish stuff I have.