This case is a perfect example of why you should NEVER change intakes on a car which was reflashed for a stock intake

Reflashes generally make power by leaning out the a/f ratio

When you add a aftermarket intake - such as in this case the HKS RS KIT - it has the effect of distorting the mass air flow reading and makes the car run very lean in the middle of the power band

Here this gentlman's mods were the following :

Works P1 Flash
HKS RS Intake
3" down pipe
Cat back exhuast


NOTE - Stock cat and fuel pump

Boost 21 psi peak taper to 19 at red line

Nothing wrong with Works flashes - JUST never add a aftermaket intake on to a flash dset up for the stock air box - be it my flash or any other flash. It is best to consult with your flash designer before doing mods. In this case the air filter swap resulted in low whp and a dangerously lean a/f curve

 

Here is our first stab with a base line Dyno Flash

We actually don't have that many good maps for this intake with the stock fuel pump and cat anymore as 99% of my customers get the upgraded walbro pump - which I highly recomend

Here he is running a bit lean

 

A bit rich and some miss fire up top - we are making some progress

 

Still needing adjustment on the a/f and ign timing - also I think its going to be time for a fresh set of plugs

 

all i have is:

works P2
HKS RS intake
custom catback exhaust

heres my dyno sheet on a mustang which is alittle conservative, i wish i had a/f ratios. by the way what kind of torque are you getting out of that car??


http://evotexas.org/scan.pdf

 

After 12 total dyno pulls and having made as much as 287 whp - which is the rannge we would expect with the stock cat in place, we realized that the car was having some significant knock issues. The customer visited a suspect Exxon station in NYC for his fill up. Looking at how the car was responding during the two hour tuning session it seemed to me that he did not get a tank of genuine 93 octane

In order to get the car to run smoothly we had to de-tune the car to actually slightly below our 91 octane california ign timing settings

I suspect bad gas and we have invited the customer to return with a new tank of fuel for further test and tune

In the meantime - we were able to get him nice power and trq gains over what he rolled in with WHILE at the same time making the a/f much richer and safer

We will revisit this customer on another day as we usually expect about 15 - 18 more whp with this combination on the stock cat

As an aisde - the fuel pump was not an issue as he had plenty of fuel supply for this power level

When tuning, it is important to listen to the motor and see how it is reacting and selct the appropraite and safe seetings

I am not interested in cars which are one hit wonders making huge dyno numbers and then later pulling timing or exploding. Saftey and smoothness are my # 1 goals.

 

nice job al. i was at the dyno the day this car was getting tuned. stock cat and bad gas were definetly the case. great job by al in figuring out the problem and giving him more power on a safe tune

 

Great diagnosis and write up on the tuning.

You mention the "bad gas" and I have seen this pop up over and over again. I am a newb and never heard of "bad gas" until I started coming to this site. What is bad gas (besides eating to many burritos ), what does it mean and how can you tell you have it? Is there a way to tell by just driving?

Also, If you tune a car using good gas and then that person goes and fills up later with crap gas what is the most likely thing to happen? Pulled timing, knock...or kaboom?

I appologize if this is a dum question but I consider myself an intelligent guy (mech. engineer) but I don't know anything about tuning and want to learn as much as I can from the professionals .

 

Sometimes are see cars that have episodes where they are unusually knock prone.

This manifests its self in the stock ecu pulling timing

In most cases we tune below the threshold of the factory ecu knock levels - this is how we maintain a super silky smooth power for which we are known

Sometimes - gasoline purchased may be stale, contanimnated or labled fraudelently and not of the proper octane level

In these cases we can quickly identify that the car is not holding power without knock - even at reduced settings

In many cases - all that is required to solve the condition is a new tank of gas

IF you have a tune on normal 93 octane for exmaple and you get some mislabeled or stale 91 octane by mistake - the ecu will quickly pull back the timing and safeguard your engine. This results in a rough power band and a noticeable "feeling" in the areas of pulled timing. Often you can see your boost gauage jumping a bit

After you renew your fuel with the proper ocatne the ecu will gradually re- calibrate itself back to the previous settings

OR you can quicken the process by resetting your ecu by disconecting your negative battery terminal

 

Thanks