randy Posted August 6, 2002 Share Posted August 6, 2002 I have had a problem for a while now with a light detonation sound coming from the engine at around 4500 RPM and went away by 5000 RPM. It was the damn fuel pump not switching to high speed mode fast enough. It apparently operates on two modes low and high. But since the boost increase it has not been able to handle the extra fuel requirement at around 4500 RPM. It shifts to high speed mode only by 5000RPM thereby starving the engine fuel for a second or so during the shift from low to high. It is simply solved by wiring a 12volt signal directly to the fuel pump so it runs on high speed mode. I feel really bad about this I hope I have not caused too much damage to my engine. Has anyone else experienced this? Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted August 12, 2002 Share Posted August 12, 2002 Randy, I don't think members on this list rate the 12V fuel pump mod much. It caused excessive fueling problems for me personally. I could easily make a device to switch outputs on at certain RPM's if people wanted this. This could effectively keep the fuel pump working at the intended 9V for low rpm and then step it up to 12V at a setting you chose on the device. But if you are happy with the 12V fuel pump mod then I guess you're O.K. :-) Regards Pete Quote Link to comment Share on other sites More sharing options...
Alex Posted August 12, 2002 Share Posted August 12, 2002 Pete, I think it would be useful to have the 9-12v cutover manually adjustable as even those of us with just a decat and/or and EBC get on boost faster than stock som being able to knock the cut over down by say 500rpm could be useful. Might give us a bit more midrange punch... Quote Link to comment Share on other sites More sharing options...
GavinL Posted August 12, 2002 Share Posted August 12, 2002 Originally posted by TRL Performance Randy, I don't think members on this list rate the 12V fuel pump mod much. It caused excessive fueling problems for me personally. I would imagine that it would heat the fuel in the tank more running the pump at full tilt.....that can't be good either. Quote Link to comment Share on other sites More sharing options...
randy Posted August 12, 2002 Author Share Posted August 12, 2002 Well guys! Since we are in the topic of fuel pump, I have some news the damn 12volt fuel pump mod did not fix my det problem completely. Now I dont have det on low boost below 1 bar when the switch over from 9-12volts happens but the moment I up the boost anything above 1.1+ and I hold the throttle at say between 5k and 6k I can hear a slight det sound must mean I am running a little lean at that specific RPM range. The det sound does not happen when I am flooring it completely just happens when I hold Revs between 5-6k on say half to 3/4 throttle. Don't know what to make of this but my injectors are not opening enough to supply the required fuel? Gavin, Regarding the fuel pump being on 12 volts I was told it is perfectly fine infact all fuel pump mods will have the pump running continuosly on 12volts. Regarding the increase of fuel temp it is probably good for me as I use a blend of Toluene and regular fuel and since Toluene needs a higher combustion temp than regular fuel for optimum efficiency it would be just fine. Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted August 12, 2002 Share Posted August 12, 2002 Originally posted by randy Regarding the increase of fuel temp it is probably good for me as I use a blend of Toluene and regular fuel and since Toluene needs a higher combustion temp than regular fuel for optimum efficiency it would be just fine. Hey so why don't you do away with your intercooler that would really raise your combustion temps!!!!! Quote Link to comment Share on other sites More sharing options...
randy Posted August 12, 2002 Author Share Posted August 12, 2002 Originally posted by Martin F Hey so why don't you do away with your intercooler that would really raise your combustion temps!!!!! What I meant was Toluene is more difficult to ignite at low temperatures and if one uses a high toluene content in their vehichles and for it to burn effectively it needs to be of a certain temperature, infact Formula 1 cars which ran high toluene content needed to have hot radiator air diverted to heat its fuel tank to 70 degrees C to assist its vaporization. If toluene is below temp it would lead to cold start problems and also affects the responsiveness of the engine due to poor burn. Because it is such an effective anti-knock fuel it also means that it is more difficult to ignite at low temperatures. Do some reading on Toluene!!! Quote Link to comment Share on other sites More sharing options...
Alex Posted August 12, 2002 Share Posted August 12, 2002 Fair point Randy, but don't forget that we use a 10% mix and F1 cars used 90+% If your running more boost than stock you'll no doubt increase the temp sufficiently. Quote Link to comment Share on other sites More sharing options...
randy Posted August 12, 2002 Author Share Posted August 12, 2002 Originally posted by Alex Holdroyd Fair point Randy, but don't forget that we use a 10% mix and F1 cars used 90+% If your running more boost than stock you'll no doubt increase the temp sufficiently. Yes F1 cars used close to 84% Toluene and the balance 16% in brew was n-heptane which has an octane rating of zero. The reason for this was F1 rocket fuel was limited to the rules to being of 102RON octane, the n-heptane is "filler" to make the fuel comply with the rules. The cars ran almost 4bar of boost or 59 psi. I am using a 40% mix of Toluene! All I was trying to say was it is perfectly fine to have your fuel pump on 12volts running continuously as do most cars and the temp increase of the fuel due to this won't affect your performance much and in my case will improve performance as I was using Toluene. Quote Link to comment Share on other sites More sharing options...
Alex Posted August 12, 2002 Share Posted August 12, 2002 Fuel pump mod won't add that much heat....its all very much nit picking IMO Why a 40% mix? Have you trimmed your fueling to match it? I'd be interested to see how the A/F mixture looks, right through the rev range. What benefit do you get from running 40%? Quote Link to comment Share on other sites More sharing options...
GavinL Posted August 12, 2002 Share Posted August 12, 2002 Originally posted by randy I have had a problem for a while now with a light detonation sound coming from the engine at around 4500 RPM and went away by 5000 RPM. It was the damn fuel pump not switching to high speed mode fast enough. It apparently operates on two modes low and high. But since the boost increase it has not been able to handle the extra fuel requirement at around 4500 RPM. It shifts to high speed mode only by 5000RPM thereby starving the engine fuel for a second or so during the shift from low to high. It is simply solved by wiring a 12volt signal directly to the fuel pump so it runs on high speed mode. I feel really bad about this I hope I have not caused too much damage to my engine. Has anyone else experienced this? Yes, people do experience det during the summertime and have to turn the boost down. I feel that we are going round in circles a bit here. I think we suggested last time that your charge temps are likely to be high and that water injection or a front mounted IC would be the way to go. Are you going to get WI or FMIC?....this policy of just throwing more fuel/octane into the engine doesn't seem to be working. regards........... Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 12, 2002 Share Posted August 12, 2002 Originally posted by randy Yes F1 cars used close to 84% Toluene and the balance 16% in brew was n-heptane which has an octane rating of zero. The reason for this was F1 rocket fuel was limited to the rules to being of 102RON octane, the n-heptane is "filler" to make the fuel comply with the rules. The cars ran almost 4bar of boost or 59 psi. I am using a 40% mix of Toluene! All I was trying to say was it is perfectly fine to have your fuel pump on 12volts running continuously as do most cars and the temp increase of the fuel due to this won't affect your performance much and in my case will improve performance as I was using Toluene. Don't forget the turbo F1 cars ran fuel at around zero degrees C when it was pumped into the tanks, to get more in. They then used a fuel heater... 40% Toluene is a wild brew for a road car, it will need a total fuelling and timing re map to make it run properly, and the stock pump may well not like it at all. Toluene is quite a "dry" chemical, and the pump may be a lot happier if you add a touch of synthetic 2 stroke oil to the fuel to lube it, and the injectors. Quote Link to comment Share on other sites More sharing options...
randy Posted August 13, 2002 Author Share Posted August 13, 2002 Originally posted by Alex Holdroyd Fuel pump mod won't add that much heat....its all very much nit picking IMO Why a 40% mix? Have you trimmed your fueling to match it? I'd be interested to see how the A/F mixture looks, right through the rev range. What benefit do you get from running 40%? Alex, I am using an octane level of 101.8 RON fuel! From what I have read the Jap spec cars have fuel and timing advance maps in the ECU for 100 RON fuel to take advantage of the high octane fuel availabe there. Hence I can't tell you how much difference it makes using this high octane fuel after re-setting your ECU. The car feels like a damn rocket!! Response is so sharp its unbelievable.:flame Dev I don't know how the air fuel map might look like as I don't have anything to check 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.
Note: Your post will require moderator approval before it will be visible.