Thread: LQ4 with new zzp 78mm polished TB?? Need some opinions!

It sounds like your ported stocker would retain the 69mm bore. That will hold you back no matter how much other porting you do to it. Take it with a grain of salt, but ZZP did a test on a nearly stock car (with 1.9 rockers) that gained two tenths from a 72mm TB. I'd say you want at least a 75mm TB with your plans, so the 78mm TB will do fine.

You are correct on the stock on retaining the 69mm bore. Thanks for the input.....I am leaning this way also. But just want some more reasurance.

Anyone else care to comment???


And with the new 78mm TB it says i have to do pcm programing...do they mean a maf tune for the ltft and the stft to get in line??

Originally Posted by TDCRacing

You are correct on the stock on retaining the 69mm bore. Thanks for the input.....I am leaning this way also. But just want some more reasurance.

Anyone else care to comment???


And with the new 78mm TB it says i have to do pcm programing...do they mean a maf tune for the ltft and the stft to get in line??

You will have to import the LQ4 MAF table if you use it. Yes the ZZP TB will require tuning, or you may find odd issues with your transmission shifting along with other things. I believe the tuning for the ZZP TB would be a little more indepth because of the TB blade size difference and how much the blade is open compared to it's actual position.

Why waste all the money on the billet TB? Just get the Northstar kit or find somebody selling their old one.

I think the ZZP TB you retain stock configuration and as Fish mentioned, use of the 99+ MAF. With the Northstar, and I could be wrong, but I believe there is no provision for the cruise control or you have to buy an additional bracket, something along those lines.

My N* setup by Trannyman, had crusie control, used the stock MAF, and maintained the PCV funtion.

Tuning required. The reason is that 10% TPS on a 69mm TB airflow is different than 10% TPS on a 78mm. Tuning is the only way to adjust for that. I'm not sure the adjustments are linear either.

I guess I should mention that easyperformance makes a TAC adapter to adjust for the TPS differences when going from a stock TB to a larger one (N* etc). This is for those that aren't able to tune.

Throttle Angle Calibrator Module Description
The Throttle Angle Calibrator (TAC) was specifically designed to alleviate the problems faced when significantly increasing the throttle body size on any OBD-II controlled engine over that of the original throttle body size. The reason for problems resides in the way the Powertrain Control Module (PCM) determines operational conditions of the engine and transmission based on throttle position. The PCM relies on the TPS signal to predict a minimum of three powertrain parameters.



One parameter is the amount of torque levels delivered to the transmission. With an oversized throttle body in place, the engine will produce significantly more power and torque at the same throttle angle due to the additional air allowed by the larger throttle body. This can cause serious problems at lower throttle settings where the PCM is not properly anticipating the higher torque produced by the engine. When the engine is producing more torque than expected, the PCM is not commanding sufficient transmission line pressures to the engagement clutches. If the clutch pressure is insufficient, then the clutches can slip, get scorched and eventually fail prematurely. The TAC will signal the PCM to the higher torque level at lower throttle angles and the PCM will respond by increasing transmission line pressures. This will result in maintaining sufficient clutch engagement and prevent clutch slippage.

Another parameter is the PCM should be crossing over from closed loop operation to open loop operation when higher air flow rates are achieved. When a significantly oversized throttle body is used in place of the original throttle body, then excessive air flow is allowed into the engine while the PCM remains in closed loop operation. The TAC signals the PCM that the effective throttle angle is greater to match the higher air flow. The PCM will then respond by switching over to open loop operation. This can save the engine from higher throttle fuel mixture control instabilities not supported by closed loop operation. In some conditions, the TAC can prevent engine damage.

A third parameter is the point at which power enrichment is triggered. The TAC signals a higher effective throttle angle than the actual position. This allows the engine to richen the fuel mixture at an air flow rate more appropriate for the larger throttle body. This also allows for more power at these throttle positions as well as holding off the onset of avoidable knock retard.

The TAC differs significantly than throttle position sensor enhancers that are currently available in the automotive aftermarket. These TPS enhancers do not affect the TPS signal at low throttle positions. They only make any changes at typically ~70% throttle and then discontinuously switch the signal to 100%. The TAC operates dramatically different. The TAC starts by giving the PCM the same idle position signal as with the original throttle body. However, immediately off idle, the TAC begins to send the PCM an increasingly higher effective throttle position relative to the original throttle body. This higher effective signal continues to increase until approximately half throttle is reached. At that point, the effective offset is gradually reduced until full throttle is reach where the TAC output is 100% just as the original throttle body. This approach means the TPS signal sent to the PCM is smooth and continuous without any drastic jumps. This results in the PCM producing smooth transitions in the control of the powertrain.

what sthe size difference in the N* to the billet ZZP?

Originally Posted by 04DetroitLS

what sthe size difference in the N* to the billet ZZP?

N* = 75mm
ZZP Billet = 78mm

ZZP sells N*s bored out to 77mm, but they cost more than the new billet TB.