hey there everyine...how is everything going....
i was just wondering...why are boosted engines so DEAD off boost....if i were able to run spark control and dial in some decent advance...would my engine feel better off boost.i am running a stock dizzy now and in order to be safe on the top end i have to rotate the dizzy a few degrees ,which in turn lowers the whole advance curve. if i were able to dial the same advance as a naturally aspirated engine when its off boost and then retard it as boost kicks in then would i have the best of both worlds
i was watching Top Gear, the episode where they tested the fq400 against a lambo in they did this test where they set up a test where the evo and some 1.6liter naturally aspirated engine were both put in 5ht gear and then when they floored it...the rented car was quicker.
i dont understand...why couldnt the evo engine pick up while it was off boost...why didnt they dial in some advance to give it some go...obviously a 2.0 naturally aspirated engine is quicker than a 1.6
any ideas guys???
running ms1,v2.2 ans thinking about msns
ignition
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jakobsladderz
- Experienced MS/Extra'er
- Posts: 170
- Joined: Tue Mar 15, 2005 10:08 pm
- Location: Ballarat, Australia
Compression Ratio, Gear ratio and vehicle mass to engine size ratio..
Generally, turbo engines run a lower compression ratio, meaning that their off-boost power-displacement ratio is slightly less than a NA engine. Especially nowdays where NA engines are pushing 10.5:1 and most turbos are less than 9:1.
Also, an EVO is a relatively heavy car for an NA 2 litre engine, whereas the 1.6 was probably better sized for the smaller engine.
Thirdly, the gear ratio on the 1.6 probably had it close to it's peak power (given its top speed was probably lower) wereas the EVO was probably well down on revs. I'd say a 1.6 on song would be making more power than a 2 litre out of its powerband.
The other thing is that a good NA cam has plenty of overlap, and wont make so much torque at lower revs (enter VVT).. A good turbo cam has much less overlap, so makes better torque low down with the turbo to help out when the revs pick up, so technically they can make more torque all the way through (if properly set-up).
The timing with an ECU will generally be optimised for the operating conditions (maybe with a lean to emissions, nevertheless close for power) and will not be limiting the torque to any great degree. If you run a mechanical advance system with no boost retard, that is a totally different story, but does not apply in the instance you mentioned since they are both EFI.
Generally, turbo engines run a lower compression ratio, meaning that their off-boost power-displacement ratio is slightly less than a NA engine. Especially nowdays where NA engines are pushing 10.5:1 and most turbos are less than 9:1.
Also, an EVO is a relatively heavy car for an NA 2 litre engine, whereas the 1.6 was probably better sized for the smaller engine.
Thirdly, the gear ratio on the 1.6 probably had it close to it's peak power (given its top speed was probably lower) wereas the EVO was probably well down on revs. I'd say a 1.6 on song would be making more power than a 2 litre out of its powerband.
The other thing is that a good NA cam has plenty of overlap, and wont make so much torque at lower revs (enter VVT).. A good turbo cam has much less overlap, so makes better torque low down with the turbo to help out when the revs pick up, so technically they can make more torque all the way through (if properly set-up).
The timing with an ECU will generally be optimised for the operating conditions (maybe with a lean to emissions, nevertheless close for power) and will not be limiting the torque to any great degree. If you run a mechanical advance system with no boost retard, that is a totally different story, but does not apply in the instance you mentioned since they are both EFI.
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