Upper pulley/heat
Thread Starter
Instructor
Joined: Jul 2018
Posts: 109
Likes: 8
Upper pulley/heat
Hello,
I have a 2016 Z06 M7, that I added an intake, ported TB, nitrous express lid,x pipe, g speed reservoir and dewitts auxiliary cooler. I am going to go ahead and put a dewitts 70mm radiator with their fan, corsa headers that I have and a catch can. While the blower is loose/off for the catch can I was thinking of adding an upper pulley. I would like to do some road course stuff with the car. I know the headers will lower boost, but wasn’t sure if I added a 2.3 pulley to get the boost back up, how much additional heat that would create, and if it would be worth it? Thanks for any information.
I have a 2016 Z06 M7, that I added an intake, ported TB, nitrous express lid,x pipe, g speed reservoir and dewitts auxiliary cooler. I am going to go ahead and put a dewitts 70mm radiator with their fan, corsa headers that I have and a catch can. While the blower is loose/off for the catch can I was thinking of adding an upper pulley. I would like to do some road course stuff with the car. I know the headers will lower boost, but wasn’t sure if I added a 2.3 pulley to get the boost back up, how much additional heat that would create, and if it would be worth it? Thanks for any information.
Last edited by Travis104; Sep 28, 2021 at 10:13 AM.
Burning Brakes
Joined: Aug 2001
Posts: 837
Likes: 388
From: Olathe KS
I did almost the same thing, put on the 2.3 upper when they did the MM catch can, CPR expansion tank, flexfuel sensor, and 2" LTs. On the street or strip the expansion tank alone does a really good job keeping temps down plus I can put ice in it for the strip if it's really hot out. On the street, even when it's 100+ here, I don't see coolant temps over 205 and that's if sitting in traffic. Normally it settles in around 185-190 coolant temps which is 15 degrees cooler than when the car was bone stock. The expansion tank doesn't help as much on a road course, it just recirculates a larger amount of rapidly warming coolant which then also takes longer to cool. A bigger HX will help the most since it sucks the heat out of the coolant, especially if you pair it with the aux cooler but the aux cooler by itself may be good enough depending on how long your sessions are.
Safety Car
Joined: Nov 2011
Posts: 3,715
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From: Norman OK
Melting Slicks
Joined: Jun 2019
Posts: 2,052
Likes: 935
From: near philly
how do exhaust headers plumbed off the exhaust valves lower boost on top of intake valves with the same compressor?
Team Owner
Joined: Aug 2011
Posts: 21,592
Likes: 1,619
From: GREER SC
I put the smaller pulley on the top and the larger on the bottom, I think it's 10% over, but not certain. If I were still doing road course I would change them back to stock. It's just makes too much for that. I only drag race now so I'm leaving them on. I can cool down between rounds most of the time. Back when I started doing Optima I got the entire " cooling kit " that DeWitt's offered at the time. Larger radiator, EOC and CAC heat exchanger. It helped, but didn't completely cure the over-heating on the road course. To fix the issue 100% you have to go to one of the kits that adds more coolers up front and get more air to them. Like the front of the ZR1. The car just has to have more air to cool it. I have seen the LG kit in person on a very hot, 105 degree, day and it really did a fantastic job. The guy even used his A/C out on the track. He was the only guy on the track that wasn't sweating half his body weight away. Lol
Safety Car
Joined: May 2000
Posts: 4,828
Likes: 357
From: Albuquerque NM
Boost is just stacked up air that the compressor is trying to force into the cylinders. The pressure (boost) increases as the engine is unable to force intake air into the chamber because of the back pressure of the combustion gasses already in the chamber. Reducing exhaust restrictions allows more exhaust to be removed, and more intake air to replace it.
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Melting Slicks
Joined: Aug 2014
Posts: 2,587
Likes: 873
A lot of people tend to get hung up on the whole higher boost is better, but what is really important is flow.
You will make more power if you can get the exhaust out quicker, and boost will fall a bit as the engine is able to take in the airflow provided by the supercharger at a faster rate. Less boost pressure makes less waste heat. Sadly, the thinner walls of the headers allow more heat into the engine bay area. Heat management as power goes up is critical to the application you are going for. You can make big numbers and be slower than the nd miata on track because your car gets too hot.
You will make more power if you can get the exhaust out quicker, and boost will fall a bit as the engine is able to take in the airflow provided by the supercharger at a faster rate. Less boost pressure makes less waste heat. Sadly, the thinner walls of the headers allow more heat into the engine bay area. Heat management as power goes up is critical to the application you are going for. You can make big numbers and be slower than the nd miata on track because your car gets too hot.
Melting Slicks
Joined: Jun 2019
Posts: 2,052
Likes: 935
From: near philly
Boost is just stacked up air that the compressor is trying to force into the cylinders. The pressure (boost) increases as the engine is unable to force intake air into the chamber because of the back pressure of the combustion gasses already in the chamber. Reducing exhaust restrictions allows more exhaust to be removed, and more intake air to replace it.
But then why would anyone put headers on.
so yeah makes sense
Melting Slicks
Joined: Aug 2014
Posts: 2,587
Likes: 873
Back pressure from exhaust is tricky and should not br confused as thr thing providing the restriction responsible for raising boost.
If there was enough back pressure to cause restriction to the supercharger this would cause problems with reversion in situations where the intake goes into vacuum. ie letting off the throttle while rpm is high going into a braking zone.
Looking at the cam specs, I think there was very little intake exhaust overlap ie less than 5 degrees which actually allows the intake charge to fully purge the cylinder prior to the exhaust valve _closing_ then allowing the intake charge to build pressure into cylinder as it is moving towards bdc before the cylinder can move down fast enough to trigger a vacuum condition.
So thr short of it is, back pressure doesn't increase boost, but rather the ability of the engine to pull air in faster ie during the overlap where the exhaust is pulling air thanks to better scavenging of headers is what reduces boost a little.
If there was enough back pressure to cause restriction to the supercharger this would cause problems with reversion in situations where the intake goes into vacuum. ie letting off the throttle while rpm is high going into a braking zone.
Looking at the cam specs, I think there was very little intake exhaust overlap ie less than 5 degrees which actually allows the intake charge to fully purge the cylinder prior to the exhaust valve _closing_ then allowing the intake charge to build pressure into cylinder as it is moving towards bdc before the cylinder can move down fast enough to trigger a vacuum condition.
So thr short of it is, back pressure doesn't increase boost, but rather the ability of the engine to pull air in faster ie during the overlap where the exhaust is pulling air thanks to better scavenging of headers is what reduces boost a little.