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I feel that our intake manifold on both is250 and 350 could use some work. There are proven result that porting the ISF manifold does provide marginal gain. If i am not mistaken about 10-15 hp.Unlike the ISF, there are no aftermarket mod for IS250/350 manifold in the market.
Right now my car is running PPE header, custom 2.5 INCH pipe, Magna-flow cat, stock resonator and Suruga loop sound exhaust with a ECU refresh running E20 Gas making about 310 HP.
With this current setup I can feel that the car hesitate little bit at Low to mid range around 2000-3500 RPM, but once pass 3500 RPM it pulls very hard to the top end. I think this is because I decided to go with 2.5 inch instead of 2.25 inch. Regardless, it still runs 0-60 less than 5 sec all day even the temp here are very high (100-110F during the day) but the wait at mid range does bug me sometimes
So I went on eBay and got a spare is350 lower intake manifold to play with. Honestly, my expectation was low haha. People from this forum are saying that it won’t do much if I don’t continue on the head and valve. But my good friend runs a machine shop and he charges me next to nothing for porting the manifold so I think it worth a shot.
I sent it in asking him to polish and expand the port if possible. Got it back a month later with a bill of 30$
The surface of the factory manifold is very rough. Polished one are very smooth and shiny and a little bigger as-well
Managed to find some free time last week so i installed it with the help of my friends. Installing process is fairly simple but it does required you to remove the pressured fuel lines so thing could go south if you are not careful.
While I was in there, I took at all the injector and clean the throttle body as well
All the process took about 2 hr and she is ready for a test drive.
The car starts right up without hesitation and idle smoothly. ECU seems happy and adjust itself without problem. Once she is warmed up we took her for a spin and did some WOT pull
Managed to do 4 WOT pull 1st 2nd gear pull
and my serpentine belt snap!!!!!!!!!
Dammit!
Went back to the shop and found out that the AC compressor froze and blew it self. It was a big mess.
Had to ordered some parts and now I have to wait and the AC compressor is not cheap.
Anyway, those WOT pull I made. My BUTT DYNO say it is much better especially at those mid range that the car lacks. It rev thru it much quicker. The car feel very strong. The engine sound changes and it seems happier at High RPM it screams louder and you can hear the air rushing thru.
With the price I paid minus the AC compressor/belt. it is definitely worth it. For you guys who lives in The States and having to pay big bucks for labor it may or may not. Or it could be a fun DIY project for you to do if you can source the part.
I really want to continue the job to its head and valve but we don't sell this model here in Thailand so no parts are available and I don't want to risk tearing the only engine I have with out spare.
Anyway, I will try to get it to the Dyno shop and see if it does really make good number like my butt feel will keep you guys posted!
With all that blackened oil / refrigerant in that compressor you need back flush solvent through the evaporator core and replace the dryer and condenser and at a minimum, the line from the compressor to the condenser. If you don't debris from the explosion will kill your new compressor.
Backflush several times and then replace condenser, lines and all that. Flush again and again it this will repeat. Pull a vacuum for several hours before recharging as the humidity there needs pulled out. I would suggest 4 hours before recharging.
GL
With all that blackened oil / refrigerant in that compressor you need back flush solvent through the evaporator core and replace the dryer and condenser and at a minimum, the line from the compressor to the condenser. If you don't debris from the explosion will kill your new compressor.
Backflush several times and then replace condenser, lines and all that. Flush again and again it this will repeat. Pull a vacuum for several hours before recharging as the humidity there needs pulled out. I would suggest 4 hours before recharging.
GL
Thanks for the tip! Will definitely have to follow your advice. A brand new Denso compressor is on its way hopefully this will be a last one i have to replaced.
I thought the clutch is designed to disengage the AC when engine is on high load. My AC compressor must be on its way out even the clutch couldnt do its job.
Why they never have an inline filter is beyond me.
As for the clutch, it appears to have 2 control mechanisms. The standard on/off at the pulley and the variable efficiency of the compressor stage. In short if the ECU doesn't disengage it electrically for over-rev protection, the unit won't protect itself.
You could add a layer of prevention but it would likely light up your dash with errors.
In short when running near WOT throttle the engine vacuum drops. Old school trick was to place a vacuum cutout switch in line with the compressor clutch. So if the vacuum drops too low during acceleration, the compressor clutch is disengaged. But I think doing this on this car would trigger CEL. It is cheap insurance if this is a true issue.
Got the car back and running. Flushing the AC system was a pain. I am glad it was over and now she is blowing cold air.
Went to the dyno today and did some pulls. I am glad that my butt dyno wasn't wrong. The car made big number even I was very surprised! But it did lose some TQ when its get warmer
These are the results from the dyno pull I did today compare with dyno run I did one year earlier with the same set up except the ported lower intake manifold
Temperature and humidity are similar and it was done at the same dyno with same SAE correction
It gained 10HP and a few TQ but I did notice that when the car heats up it lose some TQ.
Did about 6 runs and the result is pretty constant.
Hope this new info will benefit you guys in some way!
08-25-19, 09:30 PM
Ported lower intake manifold installed!
0-100
