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So I am scheduled to help a friend tune his Silvia after a ridiculous slew of upgrades. He does have to drive it on the street, but he primarily uses it to compete in Drift competition and Togue Drift events. I imagine 90% of the time on the street here he will be in vacuum. I know Andre has recommended tuning richer at .80-.83 lambda for track cars for cooling, but I was curious about thoughts on drift cars since they spend a lot of time at high revs/ rev limiter.
One of the concerns with a drift car is the entire cooling system since the car often is sideways and hence not getting good airflow directed through the radiator. This can end up with the entire engine running quite hot and this needs to be considered and managed - This is probably more of a hardware consideration than a tuning consideration but it's always valuable to look at logging from the track so you can see what temp the engine is running at.
In terms of lambda targets I would tend to treat a drift engine very much the same as a circuit race application. Boost dependent I'd expect to start tuning somewhere in the region of 0.78-0.82. For street use you'd still want to target lambda 1.0 in the cruise areas but above perhaps 4500 rpm you could tend to richen your targets again to aid engine cooling as this area is only likely to be operated in during competition.
A copy and paste from your other question which I think will apply here also.
I have tuned many pro and pro-am drift cars from SR20det, RB, 2JZ so hopefully can help.
The one thing I have noticed with people tuning drift cars etc is they get quite overly cautions due to the abuse the engine is given. Yes the motor is getting quite heavily abused but in different areas.
Because of the constant controlled loss of traction there is actually minimal load applied to the engine. Unlike a circuit car which has a lot of load applied and heat generated for big long straights etc where you may want to run richer over time or higher rpm, If you were to look at logs from drift cars they are very rarely at full throttle so there isn't as much pressure/heat etc to promote knock etc. So having to go run a richer mixture which you would usually do to reduce heat or possibility of knock isn't as necessary .
If anything all I tend to do is target a slightly richer mixture near the redline to help with reducing some heat generated and the fact the cooling system isn't as effective due to not much airflow through the radiator (As Andre mentioned). Also I leave the overrun fuel cut turned off to help with port wetting and to stop any flat spots when jumping back on the gas. Going to rich on overrun or cruise can also cause horrible flat spots and poor throttle response.
The areas I pay more attention to is the RPM limit. This is where the real damage is done, the constant hitting of the limiter and the massive RPM rate of change puts massive strain on the rods and crank. These are what usually fail on drift engines.
You need to be able to give a smooth and soft cut which won't cause a large rpm rate of change and not cut engine power down to much. Also for an SR you wan't to favor a fuel cut over ignition, if you run an ignition cut I can guarantee you will start throwing off rockers.
Andre and Chris as always the insight and experience on this site cannot be overstated. I really appreciate the things you pointed out and the little details that would be so easy to overlook. Chris the point about the lack of traction causing less load on the motor makes complete sense! Thanks so much.
Sidenote...not sure how the original post got into off topic and then duplicated here. Sorry about that!
just to expand on a point mentioned above,
what tuning precautions do you take as far as coolant temperature trims?
how aggressively do you pull timing?
do you start removing timing (and i assume adding fuel) at 100'c of a bit before or after?
do you disable the dyno cell fans get coolant temps to a high level (105-110c) and run through the rev range to confirm there is no knock?
lastly on circuit racing is there much cooling advantage from disabling the fuel cut? ie is it noticable in coolant temps?
No worries Akunochi happy to help, good luck with the project and let us know how it goes!
With most cars (street, circuit, drift etc) I will disable my IAT ignition trims while tuning, then once tuned (and no knock) I go back through and look at what the air temps were during runs on the dyno. I then will remove around 1 degree of timing per 10 degrees of temp (usually after 30 degrees I will go 2 degrees per 10) from the higher IAT end of where it was running on the dyno. These settings will also depend on what fuel im using and also the application.
For water temp I will start removing 1 degree per 10 degrees after 100 degrees. However, this is also a viscous circle because as you retard the timing you generate more heat and put more strain on the cooling system. To help with this I will start adding fuel based on throttle position and water temp to help keep the cylinder temps down (See attachment for what I mean)
I don't tend to like disabling the fans and running an engine that hot as the temp can climb fast and cause damage. Also you won't see that lack of airflow during a full throttle run on the track etc so wouldn't be very accurate.
Drift cars do tend to get up to around 100 degrees but being a short run/track it is for a very short time.
If I had a circuit car running up around those temps I would revise the cooling system.
I haven't seen a noticeable change in water temp by having the fell cut off. Usually the only difference is in throttle response.
I do though tend to run a richer mixture in a circuit car or taper to a richer mixture in higher rpm in the attempt to help with temps