Winter is here so its time to play with the computer and look at a few logs, some might find it informative and/or entertaining..

I was bored so I thought I would compare the logged boost numbers from my car at the same 1/8 mile track on a 95 and a 50 degree day. DA was 3600' and 200' for the two days. IATs for the 50 degree day were from 77-104* (27* rise), 95 degree day they were from 115-147* (32* degree rise). Thats the IAT from when the throttle hits 100% on the starting line to letting off at the 1/8 mile. The average boost is really where it picked up, the sensor is just a 2bar (14.3psi max) and peak boost would have been a little higher on the cooler day but to go from 108 to 113 in the 1/8 is a pretty good jump in power, its not all from 2psi avg increase in boost I wouldnt think.

ETs were mid 6.40s @ 108 on the 95* day, 6.17 @ 113 on the 50* day. if I run both numbers through a DA calculator the 9.40 @ 108 comes out to 9.12 @ 112.1 so thats pretty close. I'm surprised that a supercharged car is pretty close on the DA calc to an N/A car. I have noticed this all spring/summer/fall. FWIW I tune the car at the track with the in-car wideband and average a/f on each run is pretty close. The amount of fuel I had to put in the motor between the two days was a lot. To run the best on the 95* degree day I was able to run the fuel pressure at 60psi and the injector max was around 90% to get best ET/MPH. On the 50* day I had the run 70psi and 98% max duty cycle to keep it around 12.3:1 average. Thats about all it will do injector-wise so 40 degree days are out of the question

Also I'll throw in a few pics of what I calculated the ET/MPH and flywheel horsepower to be before I even had the car running in February. The flywheel hp is SAE and the ET/MPH is for a 3300lb car at sea level. Seeing it ran 9.78 @ 137 with a 1.37 60' @ 600' DA thats pretty darn close, same with the 6.17 @ 112 1/8 the other day when it was 200' DA.

Its kind of funny how it all worked out to how the car performed in reality - I didnt 'fudge' any numbers to get the sims where they are. The dyno and drag racing sims also worked out suprisingly close on the last 414 solid roller n/a car I had. I guess sometimes math does work. The most amazing thing out of everything to me is after 150 passes this year the stock connecting rods are still inside the block.

Back to figuring out next years plans

 

Its nice to see someone present facts from logs. Nice job. I guess you need a better intercooler than the OBX. Which OBX are u running (3" or 4")? Also whats the pulley combo size you running and at what RPM are u seeing 14psi? You should also think about larger injectors.

NOTE: You need to change the 1/8 ET u listed to 6 instead of 9.

 

oops, I mix up then 6s and 9s a lot

I dont think the OBX is really doing that bad. Its the 4 inch core. The 3" core I had on originally would pick up about 5-6 degrees more on an 1/8 mile pass then the 4 inch.

But yea, I have seen smaller cored 'real' intercoolers have less temp rise then this. I'm sure the aluminum alloy and fin design of the OBXs arent the same as high dollar coolers. I would really like to try a precision air/water like the TTi race kit uses but find it hard to justify the cost vs hp gain for what I'm doing.

I'm using a 7.25 crank and 3.7 blower pulley, D1 has a step up of 4.1:1 and 6600 is about as high as I go because of the stock connecting rods.

I have 57lb seimans in the car now and I'm well aware I need more, I still cant find any reliable info on the Hi-Z 75s so I'm reluctant to put down 600.00 on a set right now. The injector thing really surprised me since I never figured a pretty much stock motor would use this much fuel, its holding pressure just fine so its not running out of pump. I have an older versa fueler so I can run Low-Z injectors with the stock PCM but I'm not sure what to do at this point, some 83s and lower fuel pressure would be nice. Car looks good, runs good and is dead reliable, main problem for me is to step up a few tenths its going to cost a whole bunch of money, I think I have went about as far as I can with a lot of stock parts

 

Wow u are only running the D-1SC at 53022RPM and seeing 14psi. U still have 9000 RPM left in the blower. Im running mine at 52480 RPM and only seeing 10-11psi with some belt slippage. I used to get 7.5-8psi running at 47232RPM. I bet that 9000RPM would give u another 2-3psi if u ever wish so.

 

I had the 3.4 pully on it for one pass when it was like 60 out, made it to about 100 feet out and let off, 60' was 1.299 or something like that but it ran out of fuel quick so I swapped back to the 3.7. The 3.4 would probably be the way to go in the hot weather but the blower outlet temp will probably increase a little.

I need a better intercooler.

More injector.

Better connecting rods.

Bigger cam.

Better heads.

Less gear.

10pt cage.

More money.

*sigh*

 

What software is that? Looks pretty comprehensive. Nice info share.

 

Performance trends engine analyzer pro 3.3 and Drag race analyzer pro 2.0.

Nice software but not cheap..

 

ya i dont think a 32 degree rise is all that bad, especially when you only paid about $250 for it. you still could cut off one of the endcaps and flip it around then reweld it, that might drop down the IATs a little more.
other then that you could do some meth injection, will drop the IAT's some more and add some needed fuel.

 

Great info KP, do you have any logs of the the intake temps at the 1/4?

 

Been the meth route quite a few times in the past, I'll stick with 100% gasoline While I agree it would solve a lot of problems easily I just dont trust it, I'm sure the pumps/hardware is better then they were when I was using it but once bitten twice shy..

Here are a couple logs, I have over 150 from this year, with the black box logger from EFIlive I log every single pass I make with the car - no laptop needed One was from NvsS this year at BG when it was 97 or so degrees (running 10 teens @ 131), the IATs started at 116* on that pass and ended up at 151. The other is the best 1/4 mile (9.78) it has ran on a 70 degree day, thats the coolest temp 1/4 mile I have, the IATs started at 93* and were 127* when I let off. Doesnt gain a whole bunch if temp in the 1/4 compared to the 1/8, car is going over 110mph at that point and I imagine its moving a lot of air through the IC.

 

This is really good information. I have the same intercooler and will look at some logs when i get home. The only thing that i know that is different is the initial IAT's. Even after my burnout, mine were at most a couple degrees over ambient. But that may be the difference between my turbo barely huffing while your blower could be putting more heat into things.
I have the front of my SS cut out a lot, so i am curious to see what my final IAT's were compared to yours....in other words if the cut-out dimensions really affect things. Have an idea what your pre-IC temps are?

 

My initial IATs are probably high because the IAT sensor is in an aluminum elbow right above the upper radiator hose. Plus I have a habit of doing big burnouts and even if the bypass (pre intercooler) is open at 6000rpm in high gear i'm sure its heating things up some. If I relocated the IAT sensor closer to the outlet of the IC it would probably read quite a bit cooler when staging. I feel the IAT sensor right at the TB is a little more realistic of whats going into the engine though so I leave it there..

Its all just relative numbers anyhow, not really a good measure of IC efficiency. Best way to do that would be sensors on the inlet and outlet of the IC and I'm too lazy to do that

 

Nice info Kp, good to know that the OBX does pretty good considering. Good enough for nines is good enough for me.

But man those rods gotta come out some time....its cold, racing is over....man messing with these cars never ends.
J

 

Racing never ends here, tracks are open year round. I'll probably fool with some different injectors the next couple weeks and once thats all straightened out I'll get a new short block with some better rods an a little more cam. I'm just looking to get in the 9s at Bristol (ran 10.08 last year) and get a 5 second 1/8 for next year..

 

would it be fair to say the high iat's don't affect performance as much as you think it would?

my iat's stay around 90-95 degrees. my friend's go up to 160, but he is running a bigger blower and I think the aftercooler is a major restriction thus bringin up the iats.

 

Oh I agree….what good are the numbers if they aren’t what the engine is really seeing. I have my IAT sensor in the steel tubing right before my MAF, then a 90 then the TB. Speaking of being lazy, I have been meaning to move mine until after the meth….but I guess reading the hotter of the two is safer, so I am not hurting anything by reading the IC outlet temp before meth. Anyone know if I put the IAT sensor in the same 3” section as my meth nozzles, will it give me accurate readings?

 

Depends where your sensor is, I believe the stock Vortech setup puts the IAT sensor before the blower so naturally those numbers dont mean much. I dont think the Vortech f-body aftercooler is as much a restriction as it just doesnt have the capacity to cool a big blower but to be honest I never messed with one except on a mustang and those aftercoolers were pretty small..

I had the IAT sensor in the pipe right out of the intercooler at first and it read much lower then where its at now but I kept blowing the sensor out of the grommet so I just welded up the hole and used the sensor in the elbow right before the TB that was there originally. The 3" OBX would start at the same temp usualy but it would rise up much quicker, the 4" just having more mass makes it a lot better heat sink if anything..

Of course you want the lowest intake air temp you can get, since I only use 104 unleaded at the track I can get away with some higher IAT. A lot depends on the intake of the blower as well, at first I had the air filter blocked by a plate at the bottom and at the front so rain couldnt get to it. After I made a little 'scoop' for the filter, sort of like an ATI twin intercooler deflector, it dropped the IAT a bit also. Honestly 151 degrees on a 95+ degree air temp day isnt that bad IMO, driving the car on the highway the IAT only gets a couple degrees above air temp during cruise and takes a long time to get to 120 degrees if you nail it in 2nd gear on the highway so the IC 'looks' a lot better on the street then on the track where the starting temp is 20 degreees hotter going from a dead stop.

 

i plan on relocating my iat sensor for a more accurate reading.