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Discussion Starter · #1 · (Edited)
I just put on headers & de-cat pipe from a company which shall remain unnamed. I have a BWR s/c and Larini SE Euro style muffler.


I dynoed a few days ago and received WOEFULLY low numbers. Unfortunately I didn't dyno before with the stock system in place for comparison, but I will begin that process tomorrow.

Basically: The car is REALLY FREAKIN SLOW compared to before. It's so slow that I swear it's an NA car sometimes. Maybe a little more juice than NA. Even my lady friend noted, WITHOUT my provocation, the car felt much slower when I got on it and I struggled keeping up with my drive group today.

What could be the cause of this? Lack of back pressure? How does that work and why does it eat power? Is it with something that, with proper tuning, could actually gain power, or is the exhaust system just too damn big with or without tuning?


Stock set-up didn't sound as good, but it was very quick and ran properly.
 

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HEADERS always decrease power if not tuned for...take off the headers:thwack:
 

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So if tuned for, it will gain power? What about the lack of back pressure? I guess too little back pressure is a bad thing?
not on a boosted car. You have a wide band on it? It has been stated many times that a high flow header setup will throw off the AFR without a tune
 

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What size are the stock primary pipes and what size are the new primaries? Small primaries help low end power but can restrict the motors top end and large primaries loose low end but can help the motor to "breath" on the top end.
 

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Discussion Starter · #6 ·
not on a boosted car. You have a wide band on it? It has been stated many times that a high flow header setup will throw off the AFR without a tune
I am aware of that. I'm not sure that's the issue here, though. The codes I get are related to my cat (P0420) because obviously there is no cat. The AFR issue should arise over time, not over 50-100 miles??? I received no lean codes yet...

I've had lean codes from headers before and it never acted like this. Car would drive relatively normally with perhaps a slight loss of power from ECU compensation. This really is a considerable loss of power. Anyone with a BWR/Katana car who drives my car could immediately determine the power is far below standard.



What size are the stock primary pipes and what size are the new primaries? Small primaries help low end power but can restrict the motors top end and large primaries loose low end but can help the motor to "breath" on the top end.

I will check that...
 

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First thing you must exclude is that this is somehow related to change in gross vehicle weight caused by excessive Chinese buffet.

But seriously - how many mods have you done to your car that have either made you unhappy or required your car to be out of service for extended periods of time?

time to trade for an exige 260-poke-
 

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lol.....lean code? you cant rely on that to tell you if your tune is good or not. get yourself a wideband.
 

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get yourself a wideband.
Surely, you're not implying he needs that to hold his pants up??

BM -

Might it not help ppl if you eventually mention the brand?

NA elixes usually lose hp w/headers, as Randy stated. Unsure about FI engines, tho. Apparently, the stock design is efficient and porting it gives good results.

Do 240,260Ss use the same exh manifold as on NA cars?

Please don't leave cat uninstalled. Not much hp (3-4 NA) to be gained, as per a supplier here, illegal and overly-polluting.

Just my opinion..
 

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Discussion Starter · #10 ·
This isn't a worry for me because I can go back to stock NP... I'm just disgusted that this equipment produces such awful results. I can't believe people are expected to actually run this on an untuned ECU... I'll be getting an EFI with a wideband to combat this problem in future endeavors.

Losing a few HP is one thing, but this isn't only a few... The dyno charts await...

Yes, mods are bad for you. Actually, mods are good, so long as you do them right from the get-go.


I can't think of a good reason to disclose the company name unless somehow it's their product that is awful and not big headers in general. Both questions remain to be answered conclusively.
 

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Sorry to hear your having issues with your Mod. If you PM me with the manufacture of the Mod, I could run it by our Lotus Tech and see if he can help you in any way....Just a thought.
 

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you are making massive assumptions as well with no data to back it up. You have no idea how much damage you could be doing to your engine driving it in its current condition without knowing the AFR. good luck.
 

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Discussion Starter · #13 ·
you are making massive assumptions as well with no data to back it up. You have no idea how much damage you could be doing to your engine driving it in its current condition without knowing the AFR. good luck.

I didn't make assumptions other than that the headers have caused my predicament. My data will come from the dynos.

I'm not driving it in its current condition.

I can't pull the AFR out of my ass hole.


Appreciate the help, but...chillax?
 

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you are making massive assumptions as well with no data to back it up. You have no idea how much damage you could be doing to your engine driving it in its current condition without knowing the AFR. good luck.
+1

Mike, you realize that the sensors that are monitored by the ECU, and the conditions that cause "codes" to be "thrown" make very specific assumptions about the entire engine system, including the intake/induction system, fuel delivery, camshaft/valving parameters, compression ratio, exhaust and emissions systems. Changing any of these can invalidate a tune, and cause all sorts of havoc including generating codes when everything's fine, or not generating codes when you're about to grenade your engine.
 

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This has been discussed for several years from my searches.

Adding a header to your Lotus is likely to reduce power, hell, Charlie even had a whole thread about it.

Good thing you're not naming names, because they are not at fault.

If you want a header, expect to retune.
 

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Discussion Starter · #16 ·
Yeah, like removing a cat? I'm well aware... I'm not worried. Charliex stated a header/de-cat will be "fine" at first, and then eventually develop a lean condition. I'm reporting on immediate characteristics of these installations.

My concern is about my car losing so much power and whether its the design of the headers, the fact that I'm running aftermarket headers at all, or something else, like the ECU cutting power.
 

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Discussion Starter · #18 ·
This has been discussed for several years from my searches.

Adding a header to your Lotus is likely to reduce power, hell, Charlie even had a whole thread about it.

Good thing you're not naming names, because they are not at fault.

If you want a header, expect to retune.

I've had 3 different sets of headers. 2 from this company and one other one. I've had them on and off many times. Neither of the 1st two yielded such a profound power loss. I don't know how to explain it until I dyno. I'm not talking about a few peak HP. The entire powerband is compromised.

FWIW, this is the only set I've had "designed" for an SC application.
 

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Could it be that the culprit is something else?

Basically, dyno should be able to tell you if it's a lean/rich condition....

You tried the header with a CAT still installed?
 
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