Mt88 1st Gear January 21, 2009 Share January 21, 2009 Anyway the manual should state if the car uses regular, super/premium, or super plus/super premium. At the pumps in Japan, regular = 89RON, super/premium = 96RON and super plus/super premium = 100RON anyone know if the stated fuel in the manuals for JDM cars that regular and super/premium are the min RON rating, or is it the recommended RON rating. I'm asking because if its the recommended RON rating, there wouldn't be an performance gains if we used a higher octane fuel as the ECU will not advance the timing any further, but on the other hand, if it was the min RON, then there will be a gain in a higher octane fuel is used, but the engine will not retard the timing if a lower octane fuel is used thus increasing the risk of early detonation on high loads (taking our local octane ratings into consideration). My Jp manual say, Fuel type: Premium unleaded. It has a little disclaimer saying Regular unleaded will not fully utilized the performance as intended. As marketing diplomacy I dont think factory will state minimum because even highly tuned car like GTR will ↡ Advertisement Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 22, 2009 Author Share January 22, 2009 i thought just follow what the manual recommend, except that maybe the jdm car manual in japanese and therefore cannot read. anyway, i presume jdm cars can run on 92 as rule of thumb. Cannot. Have to check the manual. those that state super plus or super premium cannot run on our 92. Link to post Share on other sites More sharing options...
Galantspeedz Turbocharged January 22, 2009 Share January 22, 2009 My fuel cover puts min.98 My manual is in Jap so dun understand..... Link to post Share on other sites More sharing options...
DarkLord 1st Gear January 22, 2009 Share January 22, 2009 It's on a label on the fuel cover. Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 22, 2009 Author Share January 22, 2009 My Jp manual say, Fuel type: Premium unleaded. It has a little disclaimer saying Regular unleaded will not fully utilized the performance as intended. As marketing diplomacy I dont think factory will state minimum because even highly tuned car like GTR will Link to post Share on other sites More sharing options...
Falc 3rd Gear January 22, 2009 Share January 22, 2009 Are you able to monitor the timing pulled from the ECU for using RON 95 or 98? My last car i did that for Caltex 98 and the platinum, doesn't help the timing logged during runs at all. Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 22, 2009 Author Share January 22, 2009 Think thats expected. I'm into comfort nowadays so i'm going to have a look at the $/km costs for 92, 95 and 98 then decide which would be best for me. Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 22, 2009 Author Share January 22, 2009 (edited) My fuel cover puts min.98 My manual is in Jap so dun understand..... Mine has nothing.... Fortunately although my manual is in jap, the online version is in html so i opened it via babelfish Edited January 22, 2009 by Elfenstar Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 22, 2009 Author Share January 22, 2009 It's on a label on the fuel cover. Thanks for the help bro! Link to post Share on other sites More sharing options...
Mt88 1st Gear January 22, 2009 Share January 22, 2009 The Ron 95 is most likely for a local car or a manual which borrowed from local model. Those imported by AD have been adjusted to suit local requirement. Jdm car is to suit Jp norm. If fuel type stated premium, the customers there already know that is about the min req or equivalent of Ron 98 here. As general rule, a higher output engine is happier with higher octane fuel. Non performance car can make do with regular fuel as performance is not the main purpose. Modern engine with over 10.5 to 1 compression is threading thin with retard timing on regular fuel in hot temp. In high altitude areas, engine draws less air due to the reduced density of the atmosphere. That translates to reduced absolute compression in the cylinder. For every 300m or 1000ft above sea level, the RON value can go down by about 0.5. Cooler air also helps. Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 22, 2009 Author Share January 22, 2009 (edited) The Ron 95 is most likely for a local car or a manual which borrowed from local model. Those imported by AD have been adjusted to suit local requirement. Jdm car is to suit Jp norm. If fuel type stated premium, the customers there already know that is about the min req or equivalent of Ron 98 here. As general rule, a higher output engine is happier with higher octane fuel. Non performance car can make do with regular fuel as performance is not the main purpose. Modern engine with over 10.5 to 1 compression is threading thin with retard timing on regular fuel in hot temp. Yup i knew abt AD adjustments vs direct import/PI factory tunes. Mine says regular unleaded so i can run on 92 since regular in japan is 89, but in the end i guess $/km is more important to me so i'll give it a try with 95 as well (I've been running on 98 since i didn't know till the day i started this thread that mine only needed regular). In high altitude areas, engine draws less air due to the reduced density of the atmosphere. That translates to reduced absolute compression in the cylinder. For every 300m or 1000ft above sea level, the RON value can go down by about 0.5. Cooler air also helps. Mmm... this is the bit that confuses me.... are you saying that the octane level of the fuel drops at higher altitudes or that we can pump lower octane fuel at higher altitudes??? My knowledge with regards to fuel is as simple as run the fuel that your engine is tuned for (be it factory or not) instead of relying on the ECU detecting knock and retarding the timing, so this is a learning thread for me. Another couple of questions (sorry), if a non-AD JDM car says "premium/super" should they be running on 95 or 98 since premium in japan is 96. Also what about those hi-po JDM cars that require "super premium/super plus" as that is 100RON in japan, Should they get their timing retarded or would it be safe to run on 98RON since the engine will retard timing based on knock levels (at the expense of power of course). Edited January 22, 2009 by Elfenstar Link to post Share on other sites More sharing options...
Ahgongwolve Clutched January 22, 2009 Share January 22, 2009 JDM car special meh... walao same la Link to post Share on other sites More sharing options...
Boyboy 1st Gear January 22, 2009 Share January 22, 2009 should be that u can use lower octane fuel at higher altitudes. just some minor miscommunication earlier in the thread. the effective compression of the engine becomes lower cos the air is thinner than at sea level.. but for T/C cars, i'm not sure if this still applies since they can boost more to maintain the boost pressure? Link to post Share on other sites More sharing options...
Falc 3rd Gear January 22, 2009 Share January 22, 2009 (edited) It is perfectly ok (and naturally designed) for the ECU to retard timing, as long as no pinging. If u are to read off the timing retardation from the ECU, you will see that there will always be some retardation in any acceleration, partial load or WOT. The only time when there's absolutely no retardation is when your knock sensors are out. Oh and also when u are idling lah. Edited January 22, 2009 by Falc Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 25, 2009 Author Share January 25, 2009 JDM car special meh... walao same la Its not special lah old friend. Just that octane ratings and tune in japan are different localised versions Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 25, 2009 Author Share January 25, 2009 (edited) It is perfectly ok (and naturally designed) for the ECU to retard timing, as long as no pinging. If u are to read off the timing retardation from the ECU, you will see that there will always be some retardation in any acceleration, partial load or WOT. The only time when there's absolutely no retardation is when your knock sensors are out. Oh and also when u are idling lah. I know lah, but it does bring about an interesting question with regards to (for e.g.) the JDM CTR and Euro CTR. The JDM CTR puts out more power on paper, but that is with 100RON fuel, but with some timing retardation, would it be roughly the same as the Euro CTR and the higher power rating just a marketing point rather than a real advantage??? On an off topic note... ever since i drove to KL and back, my car (at about 2600kms now) seems to be getting better FC... it has been 13.1 & 13.6km/l as compared to the 12.1-12.5km/l before the trip...... Edited January 25, 2009 by Elfenstar Link to post Share on other sites More sharing options...
Iliketodrive Neutral Newbie January 25, 2009 Share January 25, 2009 I know lah, but it does bring about an interesting question with regards to (for e.g.) the JDM CTR and Euro CTR. The JDM CTR puts out more power on paper, but that is with 100RON fuel, but with some timing retardation, would it be roughly the same as the Euro CTR and the higher power rating just a marketing point rather than a real advantage??? On an off topic note... ever since i drove to KL and back, my car (at about 2600kms now) seems to be getting better FC... it has been 13.1 & 13.6km/l as compared to the 12.1-12.5km/l before the trip...... jdm & euro the engine got diff higher compression (11.7:1 vs 11.0:1) larger diameter throttle body larger and straighter intake manifolds (even with resin coating on the inner surface to reduce air resistance, like the late NSX) rerouted exhaust manifolds to reduce back-pressure. the 0-100km/h is around 1s diff. both running 98. Link to post Share on other sites More sharing options...
Elfenstar 3rd Gear January 25, 2009 Author Share January 25, 2009 jdm & euro the engine got diff higher compression (11.7:1 vs 11.0:1) larger diameter throttle body larger and straighter intake manifolds (even with resin coating on the inner surface to reduce air resistance, like the late NSX) rerouted exhaust manifolds to reduce back-pressure. the 0-100km/h is around 1s diff. both running 98. Sweet someone who seems to know about the JDM CTR. Now I have a few questions 1) What rpm does it switch to the more aggressive cam profile? 2) Does it rev higher than the Euro CTR? 3) Would I be getting right that for 1) it would be higher than the Euro CTR (5200rpm) and for 2) it would rev higher than the 8000rpm of the Euro CTR??? Just guessing based on what you posted earlier. ↡ Advertisement Link to post Share on other sites More sharing options...
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