Hi Chaps

Need some input into a decision I'm trying to make!

I race a Drakart (www.drakart.co.uk) which has a 919 RRT Fireblade engine in it! I pretty certain my engine temps are OK but only just marginally on the side of OK! I run this with a CBR 600 CDi unit too so I'm getting 1,000 more RPM before the limiter!

So, based on the fact that we rag these engines to the max and that a little restriction removed from the coolant path has to be a good thing, is there any downside to removing the thermostat? Or indeed any real upside?

I will of course spend a little more time with a cooler engine as there will be a greater volume of coolant circulating from start up, but I can handle this by spending more time warming her up!

What do you think?

all i know, some engines for car, like to run a bit hot.

I think removing the thermostat is a bit of a bodge to try and make up for the cooling system not being up to the job. I'd rather do the job properly and figure out where the limiting factor is - either needing the radiator upgrading, sorting the flow via ducting to the current one, or rerouting the cooling system if its not optimum.

quote:

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Originally posted by Steve G
I think removing the thermostat is a bit of a bodge to try and make up for the cooling system not being up to the job. I'd rather do the job properly and figure out where the limiting factor is - either needing the radiator upgrading, sorting the flow via ducting to the current one, or rerouting the cooling system if its not optimum.

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since the thermostat sits in the top hose connection, that'll be the restriction he's talking about! i guess the water pump trying to push against a flap of metal in the coolant path could cause a fairly big restriction at high engine speed

if its a race engine, the main aim is to win races, try it. if it give a little extra performance, and you win then all good, if it blows up, leave it in your next engine. i guess race engines are fairly consumable items?

i suppose the engine my run a little cooler (if it was a road car engine... i don't suppose a race engine has a chance to get cold) you will need to give it extra time to warm up before a race i guess

[Edited on 12/1/10 by blakep82]

If it runs too cool then you will lose performance so i think you will do potentially more harm by removing it. Its there to keep the engine in its optimum range and i cant believe that Honda would make it so small that it'd be a restriction

A mate of mine, year ago, removed the thermostat, replacing it with a disc with a hole, approximately 1/2 the size of the thermostat, in it.

Apparently this way restricts the flow enough to ensure cooling still takes place.

Thermostat also act as a restrictor for a reason in a lot of engines. A series for one will crack the head around the exhaust ports/valve seats due to cavitation which is why they should be fitted with a restictor if the stat is removed . Try a bottle of Water Wetter, if it's good enough for F1 ?

Yup. Some water wetter is more likely to help. If you remove the thermostat you'll take absolutely ages to warm the engine up (ie lots of time for wear and tear to occur) and you might even make the cooling work worse....

Another vote for water wetter, definitely made a difference on my 2 Kawasaki's.
The upside with water wetter is that warm up is faster whilst cooling available is increased - there is good physics behind it I believe.

never had a thermostat in my last 2 race bikes (Kawasaki ZX10r '05, Suzuki GSXR1000 '08). never had any troubles with them, also ran them without cooling fans.

It might be an idea to put an accurate number on the the temperatures (1) Cylinder head outlet (2) Radiator outlet.

If the radiator outlet temp is high it is a sign the raddiator hasn't enough area or airflow for its job.

If the cylinder head outlet temperature is high but radiator outlet temperature is low when the engine is fully warmed up you should look towards the thermostat or waterpump or engine or possible airlocks .

I might seem that removing the T/stat would aid cooling but not necessarily, if the coolant circulates too quickly it might heat away more quickly but it won't take as much heat away a.k.a. less cooling. Leave the stat and use Water Wetter as said

the thermostat restricts flow deliberately to maintain correct cooling

when having my hayabusa dyno'd the max power has always been acheived when all temps are on the hot side of ok, so id say your thermostat is doing exactly what its designed to do, so dont remove it

while as your hammering it all the time it might stay within acceptable limits will probably be on the cold side without thermostat, reducung power and worse still possibly cause damage running an engine cold on full chat, bike engines have lower tollerances than cars and must run at correct temps

aitch

Thanks for all the comments and input!

I think I'm going to procure some water wetter!