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Drfatz

Maximum Boost

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I am just curious what the maximum "safe" boost is for the 2.2 lt 4 cylinder? I know this depends on a lot of things, but let us assume that fuel supply is more then adequate for whatever we can throw at it and the turbo is infinitely efficient and can produce as much boost as you want and that the charge cooler will never let the air climb above ambient. What boost can these engines take with stock internals and the most recent Lotus head gasket before they fail? :lol:

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Graham,

Do you really expect that there is a "definte" answer ???

What I can tell you is that 1,2-1,3 bar is no problem. With boost higher than 1,4-1,6 bar you will get into serious trouble ... been there done that.

Marcus

I am just curious what the maximum "safe" boost is for the 2.2 lt 4 cylinder? I know this depends on a lot of things, but let us assume that fuel supply is more then adequate for whatever we can throw at it and the turbo is infinitely efficient and can produce as much boost as you want and that the charge cooler will never let the air climb above ambient. What boost can these engines take with stock internals and the most recent Lotus head gasket before they fail? :lol:

Marcus

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hiya,

I'll agree on that.I run 1.3 with no problem and have tried it up to 1.6 but at that point i get the feeling that something will break (gearbox) so dont go above 1.4 i would think.Remember that above 1 bar that the boost relates to power on a x 4 basis so you are talking about big differences between 1.2 and 1.4 or 1.6.

rgds

Adrian

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Hi Adrian,

Please could you expand on your comment for me ?

"Remember that above 1 bar that the boost relates to power on a x 4 basis so you are talking about big differences between 1.2 and 1.4 or 1.6."

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hiya,

I'll agree on that.I run 1.3 with no problem and have tried it up to 1.6 but at that point i get the feeling that something will break (gearbox) so dont go above 1.4 i would think.Remember that above 1 bar that the boost relates to power on a x 4 basis so you are talking about big differences between 1.2 and 1.4 or 1.6.

rgds

Adrian

I was thinking along the lines of 1.4-1.5 bar being the limit, but I have heard of people running 2.0 bar with stock internals, stock head and stock head gasket and the stock gearbox. Is this possible?

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... I would definitely say NO ...

... real cool 2,0 bar is not realistic.

This definitely would lift the head and disturb the head gasket ...

Marcus

I was thinking along the lines of 1.4-1.5 bar being the limit, but I have heard of people running 2.0 bar with stock internals, stock head and stock head gasket and the stock gearbox. Is this possible?

Marcus

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Hi Adrian,

Please could you expand on your comment for me ?

"Remember that above 1 bar that the boost relates to power on a x 4 basis so you are talking about big differences between 1.2 and 1.4 or 1.6."

OK.below 1 Bar the Turbo produces boost which has an effect on the HP Above 1 Bar this boost effect has an exponential effect on the HP produced.You are in effect quadrupling the effect of boosts below 1 Bar.

I will have a dig in my books and give you a more technical explanantion sometime the coming days when i get time

rgds

Adrian

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http://www.lotusespritforum.com/forums/ind...mp;#entry102740

here someone tried 1.7BAR - and the head gasket let go.... (post #11)

Wow...well then I had better put in an after market boost controller! Right now with a GT3071R turbo, 3" free flow exhaust, a special WC engineering chip, and the waste gate set to open at the slightest push from the solenoid she has trouble controlling the boost and I have seen it jump to over 1.8 Bar at which point I have to cut the throttle with my foot to keep the engine from going BOOM! However, other times she controls the boost pressure just fine. It seems that the boost control on these cars is terrible and so unreliable with my setup that its very dangerous. :lol:

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Graham, VERY inconsistent! That's why I went with the boost controller. I keep my overboost switch armed to 1.35 bar and my daily boost to 1.25

Artie


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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Thanks Adrian,

So, there should be a significant power gain between 1 bar and 1.1 or 1.2 than .8 and .9 for example ?

...Obviously assuming the turbo is still fairly effecient at these output levels.

Do I understand that correctly ?

OK.below 1 Bar the Turbo produces boost which has an effect on the HP Above 1 Bar this boost effect has an exponential effect on the HP produced.You are in effect quadrupling the effect of boosts below 1 Bar.

I will have a dig in my books and give you a more technical explanantion sometime the coming days when i get time

rgds

Adrian

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Any thoughts on the Greddy Profec B boost controller? I want one that doesn't have tons of bells and whistles. All I want is a reliable, relatively cheap electronic boost controller.

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Am just browsing this site (can't afford a Lotus) and found the above an interesting read. I had my ickle Smart Brabus Roadster remapped 20,000 miles ago and it runs at 1.4. Not bad for a 698cc 3 cylinder motor. BHP was reported as 127 but I've not replicated that on a rolling road.

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Any thoughts on the Greddy Profec B boost controller? I want one that doesn't have tons of bells and whistles. All I want is a reliable, relatively cheap electronic boost controller.

Graham,

the old Profec B is AWESOME, but it is no longer made, the new version is called the type S. It is the same as the old "B" controller is very simple and offers high and low boost settings. Stay away from the Spec II profec B as it has a weak stepping motor and solenoid. If you can find a genuine profec B used get it, it's worth it's weight in gold especially configuring it for these cars, you won't be dissatisfied. If new is what you prefer then I would go with the newer Profec Type S! I have used the Profec B in my RX7 for over 8 years now without changing the settings and works every single time, no variation etc. You can also look into the Blitz SBC which is an older easy to set up controller and works very well, but unlikely you can find one new, probably have to find a used one. Give me a PM and we can talk more in detail about the differences and what you need.

Artie


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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the reason i have never taken mine up the 1/4 mile is the sole reason i dont want to look like a dick when i get my ass kicked LOL, and the commentator abuse me, as a scooby/evo etc etc would beat a esprit, depressing as our cars do look fast standing still LOL


OUR CURRENT COLLECITON :- MODIFIED LOTUS ESPRIT, FULL VEILSIDE SUPRA (BEAST 409.3bhp), NEW ADDITON TO THE TROOP, 1996 S CLASS MERC (FULLY PIMPED OUT, DUB EDITION)

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