11:1 CR Race/Street Engine build - Page 4

oab_au · #46 07-07-2009, 06:25 PM

Quote:

Originally Posted by Dessertrunner

Tom he felt the problem was from heat as his extractors were about 3" away. When the engine was cold it reved out when it got hot it broke up.

Tony these sensors have a magnet in there to produce the signal. As the temp goes up the magnetic field gets less. It also loses magnetic strength with age, so when they age, and heat up,,,,,,,,,signal too weak to read.

Harvey.

Dessertrunner · #47 07-07-2009, 07:08 PM

Harvey I agree with you. If we are to get the performance out of the motors we are aiming for then its one of the issues we need to gett our head around. If as Tom mentioned the wire wasn't shielded properly and the signal get weak it would be a reciept for failure.
By the way I have posted photos of the buggy here.

oab_au · #48 07-07-2009, 08:43 PM

Quote:

Originally Posted by TomsSVX

When I talk about increasing flow, I do not mention increasing velocity for a reason. I will be working with Shotgunslade on the new engine with water pump flow rates and our sucess/failure rates at different flow rates but when I talk about flow now it is the flow withing the block. After sitting down with an open block and heads in front of me it came pretty quickly that there are a couple spots in the cooling system that have the chance to allow water to sit and stagnate. I believe it is within these sections of the engine that the water is allowed to boil. This will drop the overall system pressure allowing the water to vaporize and cause the entire system to become less efficient due to the lack of suitable pressurized water.

Tom

I think what you say here is getting close to the problem. I notice that the overheating only seems to become apparent when the race is finished and the car has slowed. I haven’t heard Dan say it overheats when it is actually racing. This is similar to what the 4lt Toyota V8 engine experiences under racing conditions. What is purposed here is that the water pump is running at speeds high enough to flow more water than the system can pass, the result is the pressure in the block can be higher than the system pressure. This allows pockets of water in the system to be above the boiling point, but not boil because of the excessive pressure in the block. When the engine slows the pressure evens out, and the pockets of water suddenly erupt as they are above the boiling point.
I think if the pump is replaced with an electric pump the flow will always match the temp, so it can’t produce higher pressures in the block.

Harvey.

SilverSpear · #49 07-08-2009, 12:48 AM

Very interesting theory. Let's say that Tom found a way to fix or go around those weak spots, and a way was found to parallel the flow of water to its temperature at different conditions... let's say while racing, the maximum flow allowable by the engine block is reached and the water keeps overheating... what is the solution here?

TomsSVX · #50 07-08-2009, 04:52 AM

Quote:

Originally Posted by SilverSpear

Very interesting theory. Let's say that Tom found a way to fix or go around those weak spots, and a way was found to parallel the flow of water to its temperature at different conditions... let's say while racing, the maximum flow allowable by the engine block is reached and the water keeps overheating... what is the solution here?

Increase the block's ability to flow. Which is partially why I am adding the aux line to the cylinder heads and also why the X-over ontop of the engine will also be looked into

Tom

SilverSpear · #51 07-08-2009, 05:21 AM

Quote:

Originally Posted by TomsSVX

Increase the block's ability to flow. Which is partially why I am adding the aux line to the cylinder heads and also why the X-over ontop of the engine will also be looked into

Tom

Appreciate if you can post pictures of this setup. Also what are the weak points that you saw in the block?

RallyBob · #52 07-08-2009, 08:51 AM

Quote:

Originally Posted by Dessertrunner

There are 2 SVX engine on drag strips over here with twin turbo's and one has had a special steel crank made for it. My guess he is the only guy in the world with an SVX engine with a steel crank.

Frank Aragona has a billet steel crank in his EG33 drag car. He told me the stock crankshaft started really flexing like crazy at about 10,500 rpms. Up to 9500 it was very stable. IIRC, Rigoli also went this route.

TomsSVX · #53 07-08-2009, 04:43 PM

Quote:

Originally Posted by SilverSpear

Appreciate if you can post pictures of this setup. Also what are the weak points that you saw in the block?

More or less the water jackets at the back of the block see little to no flow. I can only imagine that the water stagnates in these nooks and comes to a boil relatively quickly. Problem is, it is stuck there until the water flow slows down and it emerges from the corner and jumps up to the temp sensor, hence the spikes up and down.

I hope by addind auxiliary lines to the back of the cylinder heads we can assist in keeping this stagnation to a minimum and thus assist in the overheating issue. The X-over have a larger volume will assist in maintaining a desirable velocity throughout the engine instead of bottling it all up on the left side of the engine.

Tom

Dessertrunner · #54 07-08-2009, 07:21 PM

Tom its worth pointing in support of you idea that the back cyclinder on the AC compressor side is the one that overheats from what the buggy guys told me.
Tony

TomsSVX · #55 07-08-2009, 07:48 PM

Quote:

Originally Posted by Dessertrunner

Tom its worth pointing in support of you idea that the back cyclinder on the AC compressor side is the one that overheats from what the buggy guys told me.
Tony

That is the one that I had my eye on when taking a look at the block. Good to have that kind of confirmation

Tom

Dessertrunner · #56 07-09-2009, 04:00 PM

Rally Bob,
I followed up about Tom's point re the Cam sensor and the buggy guy said he will check the wiring but thinks its okay. My question to you is do you know or can you find out what cam & crank sensors the drag guys are using. If they can get the engine to rev to 10,000 then we should be okay. I just wonder if our cam sensors are not good enough past 6,500.
Tony

TomsSVX · #57 07-09-2009, 05:34 PM

Quote:

Originally Posted by Dessertrunner

Rally Bob,
I followed up about Tom's point re the Cam sensor and the buggy guy said he will check the wiring but thinks its okay. My question to you is do you know or can you find out what cam & crank sensors the drag guys are using. If they can get the engine to rev to 10,000 then we should be okay. I just wonder if our cam sensors are not good enough past 6,500.
Tony

past 6500... You mean 3250rpms? The cam is spinning half as fast as the crank and the cam sproket only has a single pick-up. Either the heat is messing with the sensor or the heat is messing with the wiring.

Tom

Dessertrunner · #58 07-09-2009, 05:53 PM

I thought Bob ment engine RPM at 10,000?

TomsSVX · #59 07-09-2009, 05:54 PM

I would imagine that the stock sensor with the proper air gap would be capable. The stock ignition system, I do not know

Tom

oab_au · #60 07-09-2009, 07:13 PM

The signal from these inductive sensors, is a sine wave that is prone to interference. The wiring from them has to be shielded, and the shield has to have a good ground to prevent it.

Harvey.