For the first few minutes of starting the car / driving my B16 definitely puts out more power. As the car warms up, power diminishes slightly.

Setup:
B16A
S2S1s
Supertech springs and retainers
Chipped ECU running BRE

What could be causing this?

 

well its not warmed up so its on higher rpms for like 5 mins than it goes down to a normal idle.... waallaa your answer.

it does the same thing to my b18 ls automatic when i wake up and drive it, i dont even have to press the gas and i go 20mph. same concept except your is 5-speed.

when i start it its on 2000 rpms than when it warms up its down to 900

 

...What??


I'm speaking in terms of gross horsepower and torque through the whole powerband. It feels like I lose 20 HP after the car is driven a bit.

 

My guess would be that heatsoak probably accounts for some of it. The differences between your closed and open-loop fuel maps might also explain the perceived difference in power output between start-up and warmed-up.

 

I've never experienced a power loss like this before in any other car.

If it makes a difference, I have an Outlaw Engineering heat gasket kit.

What determines the difference between closed and open-loop maps?

Anyone not familiar with BRE this is what the maps look like (not my exact map)

 

The chip is what is messing you up. Have a tuner look at it, and they will be able to fix your problem... I do not remember what function causes the car to do this, but I am sure it is the problem.

 

I was under the impression that the car delivers more fuel for the first couple of minutes while the car warms up to reach it's potential.

 

I've heard several things about increased fuel and advanced ignition timing upon warming up.

I've experimented and added more fuel to little effect. I am reluctant to mess with the ignition timing at the moment.

The effects of whatever is going on usually wear out before the motor reaches normal operating temperature.

 

compression and or leakdown test the cylinders, you might have a little bit weak ring seal and when the oil is cooler and thicker it does a better job keeping the compression in the cylinders possibly.

 

Good insight! I recently did a compression test and I'm around 180-185 each cylinder. 1st gen B16A BTW.

 

it seems that you need to add timing, ecu adds timing when cold, unless your really leaning out when warm.
probably 1st choice though

 

The ECU SHOULD be delivering more fuel when the engine is cold. This might explain your "loss" of power at warm up. Have a tuner check it out and see if they can find the problem.

 

the 180-185 compression..... was this cold or at operating temp?

 

180-185 cold.

I have added roughly 5% more fuel to the tables just to see if that was the situation and the change was not noticeable.

Under what conditions should timing be added?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 89s1 &raquo;</TD></TR><TR><TD CLASS="quote">compression and or leakdown test the cylinders, you might have a little bit weak ring seal and when the oil is cooler and thicker it does a better job keeping the compression in the cylinders possibly.</TD></TR></TABLE>

...Im leaning towards this as well. you know about things expanding with heat right, this coud hold true for you my friend. once warmed up, things might be a little loose and some of your compression is probably leaking.

x2 for the rings!

 

Should I do a compression test with the motor warmed up to see?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRXed &raquo;</TD></TR><TR><TD CLASS="quote">Should I do a compression test with the motor warmed up to see?</TD></TR></TABLE>

Compression tests should always be done on a warm engine, throttle 100% open, fuel pump fuse unplugged.

Also, you really shouldn't be ripping on a cold engine if you want it to last, regardless of whether it feels faster or not.

 

Ah disregard what I said about the compression test being done cold, I did it warm. Not enough sleep the past few days.

I don't beat on it when cold, it was just an observation.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRXed &raquo;</TD></TR><TR><TD CLASS="quote">I've heard several things about increased fuel and advanced ignition timing upon warming up.

I've experimented and added more fuel to little effect. I am reluctant to mess with the ignition timing at the moment.

The effects of whatever is going on usually wear out before the motor reaches normal operating temperature.</TD></TR></TABLE>

Adding more fuel will NOT give you more power. Leaner is meaner (faster and more dangerous). The ECU compensates for a lower ECT by adding more fuel, b/c a smaller % of the fuel burns at less than optimal temps.

What you're feeling is probably a result of heat soak. The ECU also compensates for this by adding less fuel, but the air/fuel ratio should stay constant. Since air density decreases with a temp increase, you effectively have less power with hotter air.

 

Happening to me big time with my gsr. Like i feel like i got a lot of torque and power when its cold but when it starts to use the o2 and all that it would decrease my performance big time. The rings and pistons only have like 5-8k bored out to. Nothing to do with the rings i think but the tune. I had a phearable ecu chip inside then i decided to change the map since it was way too rich but it had power then i changed it to enable o2 and all that. After that i lost a bunch of horsepower lol. Not really tuned completely either, going to tune it sometime this week to see if that fixes it

 

just because the rings only have 5-8k on them, doesnt mean that they are sealing 100% for the simple fact taht they are new.

you say yourself that your old chip was rich... and its a pretty fresh motor, i think you might have washed out your rings and are having the exact same problem as the OP.

again, just because the rings are new, doesnt mean they are properly seated.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by stealth50k &raquo;</TD></TR><TR><TD CLASS="quote">Happening to me big time with my gsr. Like i feel like i got a lot of torque and power when its cold but when it starts to use the o2 and all that it would decrease my performance big time. The rings and pistons only have like 5-8k bored out to. Nothing to do with the rings i think but the tune. I had a phearable ecu chip inside then i decided to change the map since it was way too rich but it had power then i changed it to enable o2 and all that. After that i lost a bunch of horsepower lol. Not really tuned completely either, going to tune it sometime this week to see if that fixes it </TD></TR></TABLE>


Funny. Enabling the O2 sensor has NO EFFECT on WOT fuel maps... but you somehow noticed a large loss of power by enabling it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote"> ecu adds timing when cold</TD></TR></TABLE>

You guys totally missed the answer right here. The ECU adds timing during warmup. You can feel the difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid96EK &raquo;</TD></TR><TR><TD CLASS="quote">


Funny. Enabling the O2 sensor has NO EFFECT on WOT fuel maps... but you somehow noticed a large loss of power by enabling it.</TD></TR></TABLE>

...so if I unplug my 2nd O2 sensor (well, leave it unplugged... since my 4-1 only allows one O2) and run my header, I shouldnt experience any diferences in the power? I thought our engines used these to properly apply the necessary corrections when the engine is running? i.e. afr, etc

I was told that I need to drill an opening for the secondary O2, in order for the engine to run at its best, since my car normally has 2, instead of one?

I get different answers from different peeps... some reputable, some are'nt.


I also had the same problem as the OP with my DX crx... it would feel torquy when cold, but I felt it had more top end once warmed up... turns out the rings were going bad and a lot was also due to the heat soak/intake set up(engine would warm the piping after a while and air density would drop greatly) but the rings for sure...

 

Great information

I can temporarily disable my O2 sensor in BRE, is it worth a try?

I'll try to advance timing just a little bit.

Heat soak isn't that much of an issue for incoming air. I have a complete outlaw engineering heat gasket set and my intake and intake manifold stay cold.

Rings are a possibility, but I am pulling good numbers on a first gen...