z-ya Posted June 21, 2012 Share Posted June 21, 2012 I'm getting close to sorting out the vintage race car. We have done some test and tunes, and also a few vintage sprint races, but we are still facing cooling issues. If the ambient temp is below 70F, we have no overheating issues. Here is the engine build: http://forums.hybridz.org/index.php/topic/96584-road-race-enduro-l28-engine-build Cooling system details: - Griffin crossflow aluminum radiator - Diesel pump with internal bypass in block plugged - Have tried 1/2, 3/4 and 1" restrictors in thermostat housing as well as 195 thermostat will 1/4" hole punched in it. - The rear coolant port on the head is routed to the thermostat housing below the thermostat/restrictor - The temperature sender is at the rear of the head measuring the temperature of the coolant coming out the head. - The cylinders are running progressively hotter moving rearward (EGT) as expected. - Using a laser gauge the temp of the outlet hose from the thermostat housing is can be almost 40F cooler than the temp of the hose coming out of the back of the head. If the ambient temp is much over 70F, in a matter of a few laps the temp at the rear of the head can climb to 220F easily. Now on cool days, there are no issues, except that the engine doesn't really get hot enough. Now if I run a thermostat, it restricts the water coming out of the rear of the head, and keeps the rest of the engine at the thermostat temperature (remember the stock sensor location is under the thermostat). But the rear of the head will run too hot in this situation. Now if I run a restrictor, the engine will not get up to temperature on cool days. If I run the outlet from the rear of the head to the top of the thermostat housing and run a thermostat, then the engine will still probably not get up to temperature on cool days. I've read this thread a number of times: http://forums.hybridz.org/index.php/topic/59029-head-cooling-on-cylinder-5-solutions/ I'm not too keen on drilling holes between the cylinder in a priceless BSR racing E31 head. According to J.R. from BSR, they ran the sensor in the rear outlet of the head without a return back to the thermostat housing. I know this for a fact because when I got the head it had a sensor fitting installed. Suggestions welcome. Thanks, Pete Quote Link to comment Share on other sites More sharing options...
johnc Posted June 21, 2012 Share Posted June 21, 2012 It sounds like the cooling system is fine except for getting the engine up to temp on cool days. 220 at the back of the head is pretty good considering a pressurized system won't see boiling until 240 or 250. Try what the truckers do, put a piece of cardboard in front the radiator and block off some of the air flow. Adjust as needed until you get the operating temp you want. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 21, 2012 Author Share Posted June 21, 2012 It sounds like the cooling system is fine except for getting the engine up to temp on cool days. 220 at the back of the head is pretty good considering a pressurized system won't see boiling until 240 or 250. Try what the truckers do, put a piece of cardboard in front the radiator and block off some of the air flow. Adjust as needed until you get the operating temp you want. John, The problem is that the temperature continues to rise at the rear of the head. On the track it climbs to 225F, then I start heading into the pits. By the time I get to the garage, it is over 235F. I have not yet seen the temperature stabilize on hot days. This is my concern. Yes, we were doing the cardboard thing on cold days, which did help that situation. Thanks, Pete Quote Link to comment Share on other sites More sharing options...
madkaw Posted June 21, 2012 Share Posted June 21, 2012 Pete, Have you tried any of the coolant products like water wetter from Redline? Or maybe trying to return the coolant to a different place like the upper hose? Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted June 21, 2012 Share Posted June 21, 2012 What # radiator cap are running? Moving up in pressure may help. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 21, 2012 Author Share Posted June 21, 2012 (edited) Pete, Have you tried any of the coolant products like water wetter from Redline? Or maybe trying to return the coolant to a different place like the upper hose? Yes, have tried the Redline product. No, I have not moved the return, but running a restrictor instead of a thermostat accomplishes the same thing. What # radiator cap are running? Moving up in pressure may help. I have tried many different pressures. Running a 18-22lb one now. It is not boiling over. Raising cooling system pressure just raises the boiling point. Edited June 21, 2012 by z-ya Quote Link to comment Share on other sites More sharing options...
johnc Posted June 21, 2012 Share Posted June 21, 2012 OK, I thought the temp stabilized at 220F. If the coolant temperature continues to rise and the cooling system is in good shape, that would indicate there isn't enough cooling capacity. The engine is putting in more BTUs then the radiator can shed. Increasing heat transfer through radiator (more fins, more tubes) is the most likely solution - assuming good airflow through the radiator and out the engine compartment. You might also want to make sure ALL the air goes through the radiator by sealing all the gaps around it. You're pretty close to having enough capacity if you're at 253F at shutdown in the pits. I'm assuming you are not running a cooling fan on the radiator. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted June 21, 2012 Share Posted June 21, 2012 My thought is why block the internal return? I have read most of the threads about coolant issues but I have never seen a reason to block it off, (At least no hard evidence.) other than keeping the pump from dead heading. But maybe I missed something. If this was not a BSR head I would have said there was casting flash blocking flow. So that just leaves you radiator/ fan combo. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 21, 2012 Author Share Posted June 21, 2012 OK, I thought the temp stabilized at 220F. If the coolant temperature continues to rise and the cooling system is in good shape, that would indicate there isn't enough cooling capacity. The engine is putting in more BTUs then the radiator can shed. Increasing heat transfer through radiator (more fins, more tubes) is the most likely solution - assuming good airflow through the radiator and out the engine compartment. You might also want to make sure ALL the air goes through the radiator by sealing all the gaps around it. You're pretty close to having enough capacity if you're at 253F at shutdown in the pits. I'm assuming you are not running a cooling fan on the radiator. John, But the temp of the coolant coming out of the thermostat housing (if I believe my laser gauge on the rubber hose) is at least 40F less than what the gauge is reading at at the rear outlet on the head. At the end of our last session the dash gauge read 230F, and the thermostat outlet hose was 160F. If I point the laser gauge at the rubber hose coming out of the rear of the head, it is about 5F less than what the dashboard gauge reads. We have done all the air flow tricks including sealing gaps, ducting, going with a smaller oil cooler (sits in front of radiator). We had a fan on it, but we removed it thinking that it was blocking flow. We also have your fiberglass hood tilted in the rear about 1" to let air out of engine compartment. The radiator is a new Arizona Z unit (Griffin), which is much larger than the Datsun competition one we were running before. The behavior is the same with either radiator. Is this all due to the fact that I am measuring temp at the rear of the head (hottest part)? In the previous engine (200HP vs 300HP) we had the sensor in the stock location. Ran 180F all day. I am assuming that return from the rear of the head mixes with the cooler water coming out of the engine at the front of the head. So I could move the sensor to the thermostat housing, but I guess I want to be sure that I'm not running the head too hot in the rear. Where did you have your sensor on your race motor? Appreciate the suggestions. Pete Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 21, 2012 Author Share Posted June 21, 2012 My thought is why block the internal return? I have read most of the threads about coolant issues but I have never seen a reason to block it off, (At least no hard evidence.) other than keeping the pump from dead heading. But maybe I missed something. If this was not a BSR head I would have said there was casting flash blocking flow. So that just leaves you radiator/ fan combo. They block the bypass in the block to get better overall flow through the engine. But then if you run a thermostat, you need to have a hole punched in it to prevent the pump from cavitating when the thermostat is closed. The bypass is blocked in the timing cover, which was done by BSR. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 21, 2012 Share Posted June 21, 2012 I am with JC, sounds like rejection doesn't equal input. Especially if you have the bypasses blocked. As to "why" you block the bypass (or any bypass): any water shunting from the hottest part of the engine to the inlet without cooling (they bypass the radiator) you only succeed in raising the inlet temperature to the engine. You decrease the radiator capacity. You must have missed that "hard evidence" in the threads. And the engine Dino testing JeffP did in this regard. The ONLY reason for a bypass is to heat the engine faster for warmup and heater operation, and to provide a circulation port for the water pump when the thermostat is closed / near closed. As Pete says, with a restrict or orifice there is no reason to use one. The secondary item that prevents cavitation in the water pump when closed is the thermostat--take a housing sometime and blow 3bar pressure in the bottom. You will see the disc and entire wax pellet assembly move. They are a spring loaded relief valve. Two small 10mm bypasses can't handle the 21gpm+ the water pump makes when quickly revved. It will pop up a bit and burp pressure. Some don't do this, and once they get gunked up this can go away as well. But generally once block pressure is above 44psi, they incrementally crack. As Pete points out BSR blocked that bypass looooong ago. It's common in most engines used for racing. Like the head cooling mods for an SBC. You reach a given performance level, everybody starts doing things very similarly-- there are few secrets, and sound engineering is sound engineering. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 21, 2012 Share Posted June 21, 2012 There is an alternative thermostat arrangement using Amot truck thermostat that sets up the radiator in a bypass loop.You take water from the thermostat outlet into Port C, water from the radiator into Port A, and the inlet to the water pump is Port B.This arrangement allows full flow at all times, mixing the coolant from the radiator (which has quite a bit of residence time) in with the outlet water for a temperature on troll on the inlet side of the engine. You size the inlet temperature for Delta-T through the engine at full load, and excess radiator doesn't become a problem under light loads as more bypasses the radiator, giving t more residence time. It's an obscure setup, but it allows the back of the head to be ported to the radiator directly independent of the thermostat. Don't know if you need it, but just putting it out there. Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted June 22, 2012 Share Posted June 22, 2012 (edited) Hi this problem has had me flat out for weeks and i have nearly got it sorted i have made some new parts up to feed the block along the hole side of the block to get cool water along the back cylinders along with head mods i have got the egt equel on all cylinders and will soon have it ready for race testing . hear are some pics. And i can not take the credit for the idear the bloke that did this 20years ago never finnished it i just found it and thought wowo that might work The idear is to run a electric water pump in to the side of the block and then remove the water out of the head like a FIA head , so far its working very well , in testing i have been able to get my 3.3 stroker to run flat out for long full lode tests with stable 180f temps ,motor is making 360hp engine on pump fuel 36deg of timing at 11.comp . Edited June 22, 2012 by PMC raceengines Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 22, 2012 Share Posted June 22, 2012 That hold-in / sealing bridge looks like a gutted old-style Amot Element! That is a neat idea for equalizing flow... That is the outlet side, no? Water will feed in from the head-side? Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted June 22, 2012 Share Posted June 22, 2012 (edited) Im testing it both ways Tony at the moment the water is going in the block , but next week i will be reverse flowing the water so in the head and out the block, i think it will work even better that way . I will be making it a one peace ally thing when it all works. Edited June 22, 2012 by PMC raceengines Quote Link to comment Share on other sites More sharing options...
didier Posted June 22, 2012 Share Posted June 22, 2012 (edited) Im testing it both ways Tony at the moment the water is going in the block , but next week i will be reverse flowing the water so in the head and out the block, i think it will work even better that way . I will be making it a one peace ally thing when it all works. I'm building a reverse flow system too, i drilled above each exhaust port, and with a Davis Craig pump, it's easy to control the flow.Two restricted hoses in the upper pockets of the head will evacuate the gazeous bubbles to the expanding tank. i answered to your message, Peter Didier Do you know this patent ? http://www.google.no/patents/US5255636 Edited June 22, 2012 by didier Quote Link to comment Share on other sites More sharing options...
B. Whisky Posted June 22, 2012 Share Posted June 22, 2012 (edited) Hmmm. The patent there lays out some real good info. Been reading up a lil bit on the head cooling threads, i think didier has this in the works for his setup? I could see that translating well into an l-series, however, it seems to make more sense in my mind to vent the head on the manifold side, and feed into the opposing side. But what diameter orifice would offer the best outlet for vapor, and not be a shunt for the coolant? Are there suitable areas on the opposite side to tap into Are those thermostats in that picture, pmc? Looks like they're staggered to fit the core plug holes? Edited June 22, 2012 by B. Whisky Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted June 22, 2012 Share Posted June 22, 2012 No there not thermostats , the water passes thro them in to the block thro the core plug holes on the manifold side i remove the core plugs and fit it in there place , so the hole block gets cool water , there is no factry water pump now its blocked off. i will post more pics and show how it all works soon . Quote Link to comment Share on other sites More sharing options...
johnc Posted June 22, 2012 Share Posted June 22, 2012 Where did you have your sensor on your race motor? On the thermostat housing in the normal place. I had a boiling over problem until I realized I was bypassing too much. Put a .063" restrictor in the bypass and solved that problem. Then lost an exhaust vale seat in number 5 from localized detonation (hot spot in the cc). Upped the system pressure to 30 psi and did the cooling system mod pulling coolant from the back of the head and between 5 and 6 up to the thermostat housing. Never had a problem after that and saw 200 to 210 temps even on 100+ degree days. Also ran a Niagra oil/water heat exchanged in the radiator so the cooling system was also taking car of cooling the oil. Never, ever saw oil temps above 250. Quote Link to comment Share on other sites More sharing options...
B. Whisky Posted June 22, 2012 Share Posted June 22, 2012 Ahh i got it now. Had to go over it a few times. Wow, thats very clever. Looking forward to emulating this. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.